8 ms·

Subscription bombing and how to mitigate it

307 points by homelessdino 7mo ago

linolevan 7mo ago
Well written piece on an attack vector I'd never thought too hard about before. Thanks for elaborating on why sending an email or two to a random person helps an attacker achieve their goal. A lot of similar articles skip over details like that.
cuu508 7mo ago
> If a bot creates an account with someone else’s email, the victim gets one email, if they ignore it that’s the end of it. The welcome email and everything after it only fires once the user verifies. As a user, I would prefer no welcome email at all.
- deleted 7mo ago
  [deleted]
- devmor 7mo ago
  Then there's no verification step, preventing the entire mechanism of you not getting spammed.
  - JoshTriplett 7mo ago
    It sounds like cuu508 didn't want the post-verification welcome, as opposed to the one-time verification message.
    - cuu508 7mo ago
      Correct.
      - sodapopcan 7mo ago
        Yes, correct. When I clicked the link I was already welcomed by the welcome page (which is, for the most part, welcomed). But then why send me another email further welcoming me? I already feel welcomed! And don't give me any of that "because it works" BS (even though that is what you are going to say). (cuu508, "you" in this instance does not mean you)
- tomjen3 7mo ago
  Yeah, thats part of why I hate "login with SERVICE". The big benefit would be not spamming me, but they always insist on getting my email. There was a time were you would have to select "sign me up for your newsletter" then you had to uncheck it. Then you had to check to not get an email and now you don't even get that choice. And lately? You have to go dig through your email because you can't set a password (looking at you Claude), so you can't filter email.
- SebastianKra 7mo ago
  I suspect everyone feels that way except SaaS providers. They could just give you a checkbox to turn the newsletter off, but they don't.
- kmoser 7mo ago
  I don't mind getting a welcome email. It also tells me when somebody has attempted to sign up for a service using my email address. What I find annoying is services that only send the welcome email once, and don't let you resend it if you never receive it.
m132 7mo ago
It's a problem, but I really dislike the solution. Putting a website with known security issues behind Cloudflare's Turnstile is comparable to enforcing code signing—works until it doesn't, and in the meantime, helps centralize power around a single legal entitiy while pissing legitimate users off. The Internet was carefully designed to withstand a nuclear war and this approach, being adopted en masse, is slowly turning it into a shadow of its former self. And despite the us-east1 and multiple Cloudflare outages of last year, we continue to stay blind to this or even rationalize it as a good thing, because that way if we're down, then so are our competitors...
- AussieWog93 7mo ago
  Honestly I really like CloudFlare as a business. There's no vendor lock-in, just a genuine good product. If they turn around later and do something evil, literally all I need to do is change the nameserver to a competitor and the users of my website won't even notice.
  - AndroTux 7mo ago
    Then you're not using any of their services besides DNS, at which point you don't need to use Cloudflare at all. As soon as you turn on any other service they offer, you need to actively migrate away. It's an inherent issue of services that actually provide a benefit. If you're saying "I can just migrate to any other nameserver" then you're telling me you have no use for Cloudflare in the first place. Because if you did, you couldn't just not use it anymore. Let's say you're using their WAF. Sure, you can just change your domain's nameserver and you've migrated away. But now you no longer have a WAF. Same for their CDN. Or their load balancer. Or their object storage. Or their CAPTCHAs.
    - thisisnow 7mo ago
      I think they also lock you into their DNS when you buy a domain from them, unlike other registrars who allow to change your NS freely. Sure, you can just transfer the domain elsewhere for a small price, but the point is they go the extra mile to force their NS, which I havent seen with other registrars.
mads_quist 7mo ago
A good old Honey Pot helped us at All Quiet "a lot" with those attacks. Basically all attacks are remediated by this. No need for Cloudflare etc.
- grey-area 7mo ago
  Can you expand on that? A separate honey pot sign up page invisible to real users, or something else?
  - mads_quist 7mo ago
    You add "hidden" inputs to your HTML form that are named like "First Name" or "Family Name". Bots will fill them out. You will either expect them to be empty or you fill by JavaScript with sth you expect. It's of course reverse-engineerable, but does the trick.
    - grey-area 7mo ago
      Thanks, I’ve seen scripted attacks bypass this sort of hidden input unfortunately (perhaps human assisted or perhaps just ignoring hidden fields).
      - mads_quist 7mo ago
        Sure, it's really basic of course.
      - jaggederest 7mo ago
        They often do actually ignore truly hidden fields (input type=hidden) but if you put them "behind" an element with css, or extremely small but still rendered, many get caught. It's similar to the cheeky prompt injection attacks people did/do against LLMs.
        grey-area 7mo ago
        Thanks.
queenkjuul 7mo ago
I had my email stolen in such an attack, i still get random "you abandoned your cart!" Emails now and then, but luckily (?) they got my credit card at the same time and i cancelled it within minutes. So it's a little annoyance, but it doesn't really make sense to me that the flood works. At least not with American credit cards that are routinely flagging my own trips to microcenter lol Editing to add: almost 100% of these emails came from the same e-commerce product, I'll have to look up which. But every site i got an email from was running the same off the shelf template.
- msephton 7mo ago
  was it ccsend.com?
  - queenkjuul 7mo ago
    I actually have no idea. I looked up one of the emails in my trash and it doesn't have any "built with" kind of thing or anything. So I can't actually tell what platform they're using, but they're definitely all the same. Here's one of the retailers in question https://utopiagoods.com/ https://utopiagoods.com/
    - msephton 7mo ago
      For me the sender email addresses contain ccsend.com
tariky 7mo ago
I had similar situation on WooCommerce shop. But it was much more signups per hour. Putting turnstile in front fixed problem. My conclusion is to move from WordPress software as fast as possible, every WordPress site I manage gets bombarded by bots.
- somat 7mo ago
  Hell every non wordpress software I manage also gets bombarded by wordpress bots.(not really, I am stretching the term to refer to wordpress attack attempts for dramatic purpose. But that still ends up being about 99% of my personal site traffic)
nubg 7mo ago
This post was written by AI, there are multiple clues. Author, why can you not use your own words? I am not sure what you meant to say, vs what is LLM garbage I could have prompted myself.
- wdutch 7mo ago
  I can't comment on if it was written by AI or not but I found the OP informative and quite dense with useful information. Nothing stood out to me as garbage.
  - nubg 7mo ago
    I agree the topic and most of the content is legit! Which makes is even more annoying. Because you don't know which are the good bits where somebody is sharing his unique insight, and which is just taken from the LLMs world knowledge.
    - chii 7mo ago
      so you are merely just prejudiced against LLM generated content, even if it was good? Why not accept that it is good, and forget about it being LLM?
      - tholm 7mo ago
        Because sounding skeptical and "clever" is more important to some people than providing meaningful and relevant insight into the topic at hand.
      - nubg 7mo ago
        ?? I literally just wrote my main complaint: > Because you don't know which are the good bits where somebody is sharing his unique insight, and which is just taken from the LLMs world knowledge.
  - radku 7mo ago
    Agreed. Personally I think about it as massaging a text with LLM is like applying filters to your pictures. The text probably have been based entirely on the internal notes and investigations and is very informative. Would it be better if the OP wrote it entirely by themselves? Not necessarily.
znnajdla 7mo ago
I absolutely refuse to use BigTech gatekeepers or useless CAPTCHAS (any sufficiently advanced bot can get around any CAPTCHA anyway). We solved this at our startup by running names through a simple LLM filter - if the name is gibberish like Px2846skxojw just block the signup. Worked surprisingly well. Of course this is easy to get around if the bot knows what you’re doing. But bots look for easy targets, as long as there are enough vibe coded crap targets on the internet they’re not going to bother with circumventing a carefully designed app.
- mads_quist 7mo ago
  Nice.
- tholm 7mo ago
  Using an LLM for this seems excessive when there are well established algorithms for detecting high entropy strings.
  - znnajdla 7mo ago
    The high entropy string option led to lots of false positives. The LLM check seems to work fine with no complaints from real users.
- snowe2010 7mo ago
  Then you’re also blocking legitimate users that don’t want to be tracked and use services like iCloud Hide my Emails
  - RobotToaster 7mo ago
    > that don’t want to be tracked >iCloud Except by apple I guess...
  - rs_rs_rs_rs_rs 7mo ago
    Those users can take their business somewhere else.
- 7mo ago
HexDecOctBin 7mo ago
I was attacked in this way a couple of months back. I use a different email address for each account (of the pattern product@example.com), and use a separate address for Git commits (like git@example.com). It was this second one that was attacked and I ended up with some 500 emails within 12 hours. Fortunately, since I don't expect anyone to actually email me on the Git address, I just put up a filter to send them all to a separate folder to go over at my leisure. After 12 hours, the pace of emails came to a halt, and then I started receiving emails to made up addresses of a American political nature on the same domain (I have wildcard alias enabled), suggesting that someone was perhaps trying to vent some frustration. This only lasted for about half an hour before the attacker seems to have given up and stopped. Strangely, I didn't receive any email during the attack which the attacker might have been trying to hide. Which has left me confused at to the purpose of this attack in the first place.
- chicagojoe 7mo ago
  I had this happen recently too, also not covering up any email activity (I combed through 3000+ spam emails). Double check that there are no forwarding rules added to your inbox and add some protection against a SIM swap. In my case, they didn't compromise any of my accounts but did attempt to open a new credit card so it would be worth double checking your credit reports.
pqdbr 7mo ago
Recently we suffered a different kind of subscription bombing: a hacker using our 'change credit card' form to 'clean' a list of thousands credit cards to see which ones would go through and approve transactions. He ran the attack from midnight to 7AM, so there were no humans watching. IPs were rotated on every single request, so no rate limiter caught it. We had Cloudflare Turnstile installed in both the sign up form and in all credit card forms. All requests were validated by Turnstile. We were running with the 'invisble' setting, and switched back to the 'recommended' setting after the incident, so I don't know if this less strict setting was to blame. Just like OP, our website - to avoid the extra hassle on users - did not require e-mail validation, specially because we send very few e-mails. We never thought this could bite us this way. Every CC he tried was charged $1 as confirmation that the CC was valid, and then immediately refunded, erroring out if the CC did not approve this $1 transaction, and that's what he used. 10% of the ~2k requests went through. Simply adding confirmation e-mail won't cut it: the hacker used - even tough he did not need it - disposable e-mail addresses services. This is a big deal. Payment processors can ban you for allowing this to happen.
- federicosimoni 7mo ago
  [flagged]
- gib444 7mo ago
  Ouch. Just one credit card change per account? This is one of those levels of monitoring that only gets put in place after such an event. Eg whole subsystem analysis - the change card feature being used 1000s of times (well, proportional to scale) in 7 hours is a massive red flag
  - eru 7mo ago
    > This is one of those levels of monitoring that only gets put in place after such an event. For a website, yes. But honestly the credit card people and their infrastructure should probably _also_ watch out for this. They'd be in a much better place to detect these.
    - 7mo ago
msephton 7mo ago
How can an affected user recover from such an attack?
- jeroenhd 7mo ago
  Report all received emails as spam, add a filter to get rid of the @domain.com emails, and probably add the entire service to the blacklist so it doesn't happen again. Probably get rid of any paid account on that service one might have laying around. If the email is targeted at a domain using mail servers from any major email provider (Gmail, Outlook), the user will probably find most emails into their spam folder anyway and the sending domain will get added to the spam list automatically. Especially if the attack hits multiple users on the same email service.
  - msephton 7mo ago
    Thanks, helpful. If I add a filter to ge rid of emails from the domain (ccsend.com) then I won't be able to mark them as spam. And what blacklist are you referring to? These are coming into my gmail inbox, as a result of some unprovoked online harassment 1.5+ years ago. Every day, still.
Jean-Philipe 7mo ago
Thanks for explaining this! I saw this happened to some of my We sites and I couldn't wrap my head around why someone would do this...
jb1991 7mo ago
One thing I have never understood in this current age is how in the world so many companies, including ones that handle confidential data like banks, don’t require a user to verify their email address after it’s entered. I have an unfortunately very generic email address that’s easy to mistype, and I am almost every day receiving order receipts for expensive vacation hotels, bank transfer or wire transfer confirmations, a very long list of things that I should not be receiving simply because the companies sending those emails never had the user verify if they entered the right email address. They are legitimate emails, they are often addressed to someone with the same first name as me but a different last name, so that person simply typed the wrong email address accidentally. It’s bonkers to me that there’s any developers out there working for these companies that never thought to implement simple email verification.
- Gigachad 7mo ago
  Because confirming the email introduces friction. And everyone is optimising for low friction even if it risks private data leaks, which you can always blame on the user for typing their email wrong.
- pprotas 7mo ago
  This is intentional. Email verification is friction, so it gives users a chance to reconsider whether their purchase is really necessary. This is bad for business, because they’d prefer if you were impulsive. Also, people usually type their emails correctly, especially these days with auto-fill. So not sending confirmation emails is optimizing for the happy path.
  - jb1991 7mo ago
    Not just talking about purchases. I receive transaction details with bank numbers for wire transfers around the world. It’s ridiculous. I was once even sent all of the legal proceedings for a court case by a lawyer who was sent to the wrong address.
  - expedition32 7mo ago
    I just recently got a Visa debit card and I have to verify every purchase in my bank app. Absolutely 100 percent fraud and security proof. However as you it is an extra step and I imagine many retailers have done the math between fraud and friction...
chw9e 7mo ago
This happened to me several years ago. I got signed up to probably 700 newsletters overnight. In the middle of all of the sign ups there was activity on my airbnb account where my notification settings were changed. when i checked my airbnb i noticed that someone had created a fake listing under my account and disabled booking notifications for it. a real multi-layer scam where the hacker would be making money off a fake listing on someone else's account who would probably never even realize it.
- Gigachad 7mo ago
  I’d be probably safe against this because I have an email filter set so anything with an unsubscribe link gets moved to spam. Account notification emails don’t have unsubscribes while pretty much all junk does.
  - noname120 7mo ago
    I receive a bunch of transactional emails with an unsubscribe button at the bottom. Unsubscribing of course does nothing to stop the transactional emails but the last thing I want is them to go to spams.
- duckmysick 7mo ago
  How did they access your Airbnb account?
mfi 7mo ago
I work the email security company xorlab[0], where my colleagues and I did a thorough analysis of real subscription/email bombing waves that we saw at our customers[1]. Here are some interesting additional information from the attacks we analyzed: * Email bombing as a service is a thing, where you can buy 10,000 credits for $10 and easily bomb target inboxes with over 2000 emails per hour. * Most all email bombing attacks starts in the morning, between 8-10. * Most common day of attack is Friday [0] https://www.xorlab.com/en/ https://www.xorlab.com/en/ [1] https://www.xorlab.com/en/blog/from-chaos-to-control-insights-from-24-email-bombing-waves https://www.xorlab.com/en/blog/from-chaos-to-control-insight...
paaradise 7mo ago
> that meant each victim received three emails from us in under a minute: > Verify your email address > Welcome to Suga > Reset your password > Three emails they never asked for, from a product they may never have heard of. We were just one of potentially hundreds of sites being hit at the same time. @homelessdino Why would you send welcome and reset to some victim that DID NOT verify?
- simonkagedal 7mo ago
  This is being addressed in the article. The service no longer does this, and he apologizes.
CrzyLngPwd 7mo ago
We experienced a similar thing; Thousands of new accounts were being created over a short period, but it was Amazon SES sending us a warning about complaint numbers that woke us up to it. We added a captcha and used a disposable email checking service to get rid of it.
s99850 7mo ago
[flagged]
shreyssh 7mo ago
[flagged]
shreyssh 7mo ago
[flagged]
avian 7mo ago
> The goal [...] to flood the victim’s inbox with so much noise that they can’t find the emails that actually matter. > While the victim is drowning [...] the attacker is doing something else. In the past months some personal mail accounts on a mail server I administer were victim of something that looked similar to what's described here. Hundreds of mails apparently originating from various (legit-looking) random public web services, support requests, issue trackers, web contact forms etc. For example, a good part of them was from Virginia Department of Motor Vehicles (as in something like "thank you for filing a document #123 with us"). To make things even weirder, they were not sent directly to the address, but according to message headers were bounced through Google Groups (each time I checked the relevant group was already deleted). So as far as I can tell it was not the mail address hosted on my server that was being entered into those websites. No phishing links, no attached malware, no short advertisements snuck into a text field etc. Just a huge amount of automated replies from "noreply@" legit entities. I've seen several of these attacks and spent some time investigating them. To my knowledge these were not associated with any other malicious activity, like the author of the article mentions. If anything they were just a denial-of-service attack on a mail box (as in, making the human user trawl through garbage, the mail volume was far from saturating the server itself). What exactly would be a motivation for that I can't tell, except making the life of a small mail server admin even harder than it already is.
motbus3 7mo ago
I know this is ain't new But I am tired of people turning everything into weapons When I started working I wanted to see things being built and evolve Now, every mofo just wants a grant to ---- innocent kids in school.
aservus 7mo ago
The irony is that the services most vulnerable to this are the ones that collect the most email/data in the first place. Minimal data collection is the best mitigation.
thisisnow 7mo ago
Interesting, until it turned into an ad for Cloudflare, it spreads like plague on the internet, slowing everyday down, forcing JS and trying to pull every single datapoint from your browser. Is this really the _only_ solution?
z3t4 7mo ago
Could ask new users to send an email on a generated temp adress before sending the confirm e-mail. I do think e-mail should be not only opt-in, but also optional!
jiehong 7mo ago
I think it’s time to stop using emails in general for all of that. What’s the alternative, though? What if each service generates a link to a uuid url where all new message will be displayed? The user can rss subscribe to that. So the user doesn’t receives anything.
SophieVeldman 7mo ago
[flagged]
dgellow 7mo ago
Oh that’s interesting. I think that matches perfectly with an experience I had with a micro saas I run. I first thought people discovered it organically because it started with just a few signups throughout the weekend, then eventually escalated to multiple an hour. None of the accounts were active but email addresses didn’t look too odd and they weren’t bouncing. I eventually added a captcha that seems to have been effective, but that was a surprising experience because there is nothing you can use that saas for anything nefarious as far as I’m aware
croemer 7mo ago
Incidentally, email bombing was likely used in the axios attack to bury some important security notifications: https://github.com/axios/axios/discussions/10612 https://github.com/axios/axios/discussions/10612
jeninho 7mo ago
[dead]
petercooper 7mo ago
As a newsletter company, we've dealt with this for over a decade now since we do the right thing and do double opt-in which involves sending the subscriber an email on signup. Until a few years ago, IP reputation was a good defence against this. The bad traffic almost entirely came from IP addresses in certain countries or from datacenter IPs we could block. Nowadays, that doesn't work due to the prevalence of VPNs, so many legitimate users appear to come from low reputation IPs. Turnstile is a reasonable solution in its normal form, though the 'invisible' option still lets a lot of them through. Another thing that works, surprisingly, is looking for "webdriver" usage. Despite being easy to strip out webdriver fingerprints, we find that the majority of automated attempts do not bother to do this. Adding more steps, honeypots (with an immediate short term IP ban), etc. also have an impact. It becomes a game of piling up numerous defences in a sort of "Swiss cheese model".
- aftbit 7mo ago
  That's a fun cobra effect. Age verification ("intended" to make children safer online, if you take the most charitable view) forces more and more people to use VPNs, which overall degrades the value of IP reputation as a signal, forcing providers to accept less reputable IPs because real customers come from them, which means that providers are more vulnerable to attacks that can be used to target children.
  - observationist 7mo ago
    The point isn't protection from attacks that target children, it's gatekeeping content to keep it away from children. Providers are more vulnerable to attacks, overall, because of that gatekeeping, because of ht inevitable use of tools like VPNs and proxies to bypass the mechanisms being used. This sort of anti-anonymity is specifically and precisely targeted at decreasing the security of individuals, subjecting them to surveillance and control by the state. It has nothing to do with "protecting the children" and never did. The four horsemen of the infocalypse are always about power grabs, they're never about actually protecting citizens, or children, or securing a country or region.
razkaplan 7mo ago
[flagged]
- usernamed7 7mo ago
  as expected, this is slop
perching_aix 7mo ago
I'm not sure this is on the email address form providing service's side to combat. This is an inherent issue to email. Email should evolve finally, or disappear.
rglullis 7mo ago
So that explains the handful of random sign-ups I am getting on Communick. The pattern fits exactly what I am seeing as well (3-4 signups in an hour, weird usernames and gmail/hotmail addresses with lots of "." that are usually ignored. At least on my case the mitigation comes with my obsession in not collecting any unnecessary data. Email address are optional and only used if you are already a paying subscriber. Maybe I should just remove it from the sign-up form altogether and use it as a honeypot.
tmarice 7mo ago
I don't really understand the captcha hate, it's table stakes for any public-facing form. You need to pick a point on the "Ease of signup" vs. "Security" curve, and email signup + captcha seems to be the sweet spot. I haven't seen any proof that the big ones (Google, CF) can be easily and automatically bypassed, and would love to learn more if someone has evidence to the contrary.
- LEDThereBeLight 7mo ago
  Anyone who’s trying to make money through stuff like this (versus just experimenting) is using one of the many paid captcha-solving APIs, which cost a cent or two per solved captcha.
- withinboredom 7mo ago
  My blog does a proof-of-work before submission (withinboredom.info) in your browser. It'll use a fair bit of cpu power, but should only take a few seconds to complete. For an attacker... that's quite slow and self-limiting.
  - eduction 7mo ago
    I did Ctrl-F on "proof-of-work" in this thread to see if anyone had tried this, you seem to be the only one. Seems like a good precaution before sending even a verification email. Did you have to roll your own or was there some proof of work library you were able to use? Update: Ah, found the code - https://withinboredom.info/posts/how-this-blog-actually-works/#1-subscribing-with-proof-of-work-rate-limiting https://withinboredom.info/posts/how-this-blog-actually-work...
gadders 7mo ago
I had this happen to me at the weekend. Someone bought a train ticket using my debit card and then (I assume) in an attempt to hide the copy of the ticket that was emailed to me, I was subscription bombed at the same time.
arafeq 7mo ago
[flagged]
veyh 7mo ago
Oh, that actually explains a lot. I used to offer a 7-day free trial for one of my apps that you could sign up for with an email, and the vast majority of the licenses were never used. The app wasn't even downloaded that many times. I stopped offering the trial since I figured it was not useful for a relatively cheap (19 EUR) app that has a 30-day money-back guarantee anyway. (It can also be used for 15 mins without a license, but requires a restart after that.)
halapro 7mo ago
Back in my day people would sign you up to porn newsletters and those would not ask twice.
frankest 7mo ago
I has gone down recently (or they switched to other sites), but it was coming from EU VPN addresses at first before they got lazy and used mostly Russian IPs.
patrickRyu 7mo ago
[flagged]
tantalor 7mo ago
Mitigating this is kind of pointless, because so many sites are vulnerable to this. I got subscription bombed from about a dozen .gov sites a while back. Healthcare.gov, Social Security Administration, WTC Health Program, FDA, National Institute of Mental Health, Medicare.gov. It's very easy for attackers to do this. Putting in effort to solve this for one site, and expecting any impact, is like trying to empty the ocean with a teaspoon.
- alsetmusic 7mo ago
  You mitigate because you want to be responsible and not contribute to a problem. One person has to be the first to do something better before it can become a thing that is a best practice throughout an entire industry.
  - tantalor 7mo ago
    Like I said, it's pointless.
    - alsetmusic 7mo ago
      Oh, sorry. I didn’t realize you were commenting from a position of selfishness. For people who want to put in a little more effort in hope of inspiring others to do the same and maybe eventually encourage positive change, it’s great.
pagecalm 7mo ago
Honestly just don't send anything past the verification email until the address is confirmed. A lot of the other fixes here are working around what's really just auth libraries trusting the address on signup. Feels like that's the thing worth fixing first.
fyrn_ 7mo ago
The attack doesn't work on hey mail, since new senders have to be accepted before they go the inbox. Presumably Google or whatever is already whitelisted and just goes through
xkbear89 7mo ago
[flagged]

307 points by homelessdino 7mo ago

Well written piece on an attack vector I'd never thought too hard about before. Thanks for elaborating on why sending an email or two to a random person helps an attacker achieve their goal. A lot of similar articles skip over details like that.

cuu508 7mo ago

> If a bot creates an account with someone else’s email, the victim gets one email, if they ignore it that’s the end of it. The welcome email and everything after it only fires once the user verifies. As a user, I would prefer no welcome email at all.

deleted 7mo ago
[deleted]
devmor 7mo ago
Then there's no verification step, preventing the entire mechanism of you not getting spammed.
- JoshTriplett 7mo ago
  It sounds like cuu508 didn't want the post-verification welcome, as opposed to the one-time verification message.
  - cuu508 7mo ago
    Correct.
    - sodapopcan 7mo ago
      Yes, correct. When I clicked the link I was already welcomed by the welcome page (which is, for the most part, welcomed). But then why send me another email further welcoming me? I already feel welcomed! And don't give me any of that "because it works" BS (even though that is what you are going to say). (cuu508, "you" in this instance does not mean you)
tomjen3 7mo ago
Yeah, thats part of why I hate "login with SERVICE". The big benefit would be not spamming me, but they always insist on getting my email. There was a time were you would have to select "sign me up for your newsletter" then you had to uncheck it. Then you had to check to not get an email and now you don't even get that choice. And lately? You have to go dig through your email because you can't set a password (looking at you Claude), so you can't filter email.
SebastianKra 7mo ago
I suspect everyone feels that way except SaaS providers. They could just give you a checkbox to turn the newsletter off, but they don't.
kmoser 7mo ago
I don't mind getting a welcome email. It also tells me when somebody has attempted to sign up for a service using my email address. What I find annoying is services that only send the welcome email once, and don't let you resend it if you never receive it.

m132 7mo ago

It's a problem, but I really dislike the solution. Putting a website with known security issues behind Cloudflare's Turnstile is comparable to enforcing code signing—works until it doesn't, and in the meantime, helps centralize power around a single legal entitiy while pissing legitimate users off. The Internet was carefully designed to withstand a nuclear war and this approach, being adopted en masse, is slowly turning it into a shadow of its former self. And despite the us-east1 and multiple Cloudflare outages of last year, we continue to stay blind to this or even rationalize it as a good thing, because that way if we're down, then so are our competitors...

AussieWog93 7mo ago
Honestly I really like CloudFlare as a business. There's no vendor lock-in, just a genuine good product. If they turn around later and do something evil, literally all I need to do is change the nameserver to a competitor and the users of my website won't even notice.
- AndroTux 7mo ago
  Then you're not using any of their services besides DNS, at which point you don't need to use Cloudflare at all. As soon as you turn on any other service they offer, you need to actively migrate away. It's an inherent issue of services that actually provide a benefit. If you're saying "I can just migrate to any other nameserver" then you're telling me you have no use for Cloudflare in the first place. Because if you did, you couldn't just not use it anymore. Let's say you're using their WAF. Sure, you can just change your domain's nameserver and you've migrated away. But now you no longer have a WAF. Same for their CDN. Or their load balancer. Or their object storage. Or their CAPTCHAs.
  - thisisnow 7mo ago
    I think they also lock you into their DNS when you buy a domain from them, unlike other registrars who allow to change your NS freely. Sure, you can just transfer the domain elsewhere for a small price, but the point is they go the extra mile to force their NS, which I havent seen with other registrars.

mads_quist 7mo ago

A good old Honey Pot helped us at All Quiet "a lot" with those attacks. Basically all attacks are remediated by this. No need for Cloudflare etc.

grey-area 7mo ago
Can you expand on that? A separate honey pot sign up page invisible to real users, or something else?
- mads_quist 7mo ago
  You add "hidden" inputs to your HTML form that are named like "First Name" or "Family Name". Bots will fill them out. You will either expect them to be empty or you fill by JavaScript with sth you expect. It's of course reverse-engineerable, but does the trick.
  - grey-area 7mo ago
    Thanks, I’ve seen scripted attacks bypass this sort of hidden input unfortunately (perhaps human assisted or perhaps just ignoring hidden fields).
    - mads_quist 7mo ago
      Sure, it's really basic of course.
    - jaggederest 7mo ago
      They often do actually ignore truly hidden fields (input type=hidden) but if you put them "behind" an element with css, or extremely small but still rendered, many get caught. It's similar to the cheeky prompt injection attacks people did/do against LLMs.
      - grey-area 7mo ago
        Thanks.

queenkjuul 7mo ago

I had my email stolen in such an attack, i still get random "you abandoned your cart!" Emails now and then, but luckily (?) they got my credit card at the same time and i cancelled it within minutes. So it's a little annoyance, but it doesn't really make sense to me that the flood works. At least not with American credit cards that are routinely flagging my own trips to microcenter lol Editing to add: almost 100% of these emails came from the same e-commerce product, I'll have to look up which. But every site i got an email from was running the same off the shelf template.

msephton 7mo ago
was it ccsend.com?
- queenkjuul 7mo ago
  I actually have no idea. I looked up one of the emails in my trash and it doesn't have any "built with" kind of thing or anything. So I can't actually tell what platform they're using, but they're definitely all the same. Here's one of the retailers in question https://utopiagoods.com/ https://utopiagoods.com/
  - msephton 7mo ago
    For me the sender email addresses contain ccsend.com

tariky 7mo ago

I had similar situation on WooCommerce shop. But it was much more signups per hour. Putting turnstile in front fixed problem. My conclusion is to move from WordPress software as fast as possible, every WordPress site I manage gets bombarded by bots.

somat 7mo ago
Hell every non wordpress software I manage also gets bombarded by wordpress bots.(not really, I am stretching the term to refer to wordpress attack attempts for dramatic purpose. But that still ends up being about 99% of my personal site traffic)

nubg 7mo ago

This post was written by AI, there are multiple clues. Author, why can you not use your own words? I am not sure what you meant to say, vs what is LLM garbage I could have prompted myself.

wdutch 7mo ago
I can't comment on if it was written by AI or not but I found the OP informative and quite dense with useful information. Nothing stood out to me as garbage.
- nubg 7mo ago
  I agree the topic and most of the content is legit! Which makes is even more annoying. Because you don't know which are the good bits where somebody is sharing his unique insight, and which is just taken from the LLMs world knowledge.
  - chii 7mo ago
    so you are merely just prejudiced against LLM generated content, even if it was good? Why not accept that it is good, and forget about it being LLM?
    - tholm 7mo ago
      Because sounding skeptical and "clever" is more important to some people than providing meaningful and relevant insight into the topic at hand.
    - nubg 7mo ago
      ?? I literally just wrote my main complaint: > Because you don't know which are the good bits where somebody is sharing his unique insight, and which is just taken from the LLMs world knowledge.
- radku 7mo ago
  Agreed. Personally I think about it as massaging a text with LLM is like applying filters to your pictures. The text probably have been based entirely on the internal notes and investigations and is very informative. Would it be better if the OP wrote it entirely by themselves? Not necessarily.

znnajdla 7mo ago

I absolutely refuse to use BigTech gatekeepers or useless CAPTCHAS (any sufficiently advanced bot can get around any CAPTCHA anyway). We solved this at our startup by running names through a simple LLM filter - if the name is gibberish like Px2846skxojw just block the signup. Worked surprisingly well. Of course this is easy to get around if the bot knows what you’re doing. But bots look for easy targets, as long as there are enough vibe coded crap targets on the internet they’re not going to bother with circumventing a carefully designed app.

mads_quist 7mo ago
Nice.
tholm 7mo ago
Using an LLM for this seems excessive when there are well established algorithms for detecting high entropy strings.
- znnajdla 7mo ago
  The high entropy string option led to lots of false positives. The LLM check seems to work fine with no complaints from real users.
snowe2010 7mo ago
Then you’re also blocking legitimate users that don’t want to be tracked and use services like iCloud Hide my Emails
- RobotToaster 7mo ago
  > that don’t want to be tracked >iCloud Except by apple I guess...
- rs_rs_rs_rs_rs 7mo ago
  Those users can take their business somewhere else.
7mo ago

HexDecOctBin 7mo ago

I was attacked in this way a couple of months back. I use a different email address for each account (of the pattern product@example.com), and use a separate address for Git commits (like git@example.com). It was this second one that was attacked and I ended up with some 500 emails within 12 hours. Fortunately, since I don't expect anyone to actually email me on the Git address, I just put up a filter to send them all to a separate folder to go over at my leisure. After 12 hours, the pace of emails came to a halt, and then I started receiving emails to made up addresses of a American political nature on the same domain (I have wildcard alias enabled), suggesting that someone was perhaps trying to vent some frustration. This only lasted for about half an hour before the attacker seems to have given up and stopped. Strangely, I didn't receive any email during the attack which the attacker might have been trying to hide. Which has left me confused at to the purpose of this attack in the first place.

chicagojoe 7mo ago
I had this happen recently too, also not covering up any email activity (I combed through 3000+ spam emails). Double check that there are no forwarding rules added to your inbox and add some protection against a SIM swap. In my case, they didn't compromise any of my accounts but did attempt to open a new credit card so it would be worth double checking your credit reports.

pqdbr 7mo ago

Recently we suffered a different kind of subscription bombing: a hacker using our 'change credit card' form to 'clean' a list of thousands credit cards to see which ones would go through and approve transactions. He ran the attack from midnight to 7AM, so there were no humans watching. IPs were rotated on every single request, so no rate limiter caught it. We had Cloudflare Turnstile installed in both the sign up form and in all credit card forms. All requests were validated by Turnstile. We were running with the 'invisble' setting, and switched back to the 'recommended' setting after the incident, so I don't know if this less strict setting was to blame. Just like OP, our website - to avoid the extra hassle on users - did not require e-mail validation, specially because we send very few e-mails. We never thought this could bite us this way. Every CC he tried was charged $1 as confirmation that the CC was valid, and then immediately refunded, erroring out if the CC did not approve this $1 transaction, and that's what he used. 10% of the ~2k requests went through. Simply adding confirmation e-mail won't cut it: the hacker used - even tough he did not need it - disposable e-mail addresses services. This is a big deal. Payment processors can ban you for allowing this to happen.

federicosimoni 7mo ago
[flagged]
gib444 7mo ago
Ouch. Just one credit card change per account? This is one of those levels of monitoring that only gets put in place after such an event. Eg whole subsystem analysis - the change card feature being used 1000s of times (well, proportional to scale) in 7 hours is a massive red flag
- eru 7mo ago
  > This is one of those levels of monitoring that only gets put in place after such an event. For a website, yes. But honestly the credit card people and their infrastructure should probably _also_ watch out for this. They'd be in a much better place to detect these.
  - 7mo ago

msephton 7mo ago

How can an affected user recover from such an attack?

jeroenhd 7mo ago
Report all received emails as spam, add a filter to get rid of the @domain.com emails, and probably add the entire service to the blacklist so it doesn't happen again. Probably get rid of any paid account on that service one might have laying around. If the email is targeted at a domain using mail servers from any major email provider (Gmail, Outlook), the user will probably find most emails into their spam folder anyway and the sending domain will get added to the spam list automatically. Especially if the attack hits multiple users on the same email service.
- msephton 7mo ago
  Thanks, helpful. If I add a filter to ge rid of emails from the domain (ccsend.com) then I won't be able to mark them as spam. And what blacklist are you referring to? These are coming into my gmail inbox, as a result of some unprovoked online harassment 1.5+ years ago. Every day, still.

Jean-Philipe 7mo ago

Thanks for explaining this! I saw this happened to some of my We sites and I couldn't wrap my head around why someone would do this...

jb1991 7mo ago

One thing I have never understood in this current age is how in the world so many companies, including ones that handle confidential data like banks, don’t require a user to verify their email address after it’s entered. I have an unfortunately very generic email address that’s easy to mistype, and I am almost every day receiving order receipts for expensive vacation hotels, bank transfer or wire transfer confirmations, a very long list of things that I should not be receiving simply because the companies sending those emails never had the user verify if they entered the right email address. They are legitimate emails, they are often addressed to someone with the same first name as me but a different last name, so that person simply typed the wrong email address accidentally. It’s bonkers to me that there’s any developers out there working for these companies that never thought to implement simple email verification.

Gigachad 7mo ago
Because confirming the email introduces friction. And everyone is optimising for low friction even if it risks private data leaks, which you can always blame on the user for typing their email wrong.
pprotas 7mo ago
This is intentional. Email verification is friction, so it gives users a chance to reconsider whether their purchase is really necessary. This is bad for business, because they’d prefer if you were impulsive. Also, people usually type their emails correctly, especially these days with auto-fill. So not sending confirmation emails is optimizing for the happy path.
- jb1991 7mo ago
  Not just talking about purchases. I receive transaction details with bank numbers for wire transfers around the world. It’s ridiculous. I was once even sent all of the legal proceedings for a court case by a lawyer who was sent to the wrong address.
- expedition32 7mo ago
  I just recently got a Visa debit card and I have to verify every purchase in my bank app. Absolutely 100 percent fraud and security proof. However as you it is an extra step and I imagine many retailers have done the math between fraud and friction...

chw9e 7mo ago

This happened to me several years ago. I got signed up to probably 700 newsletters overnight. In the middle of all of the sign ups there was activity on my airbnb account where my notification settings were changed. when i checked my airbnb i noticed that someone had created a fake listing under my account and disabled booking notifications for it. a real multi-layer scam where the hacker would be making money off a fake listing on someone else's account who would probably never even realize it.

Gigachad 7mo ago
I’d be probably safe against this because I have an email filter set so anything with an unsubscribe link gets moved to spam. Account notification emails don’t have unsubscribes while pretty much all junk does.
- noname120 7mo ago
  I receive a bunch of transactional emails with an unsubscribe button at the bottom. Unsubscribing of course does nothing to stop the transactional emails but the last thing I want is them to go to spams.
duckmysick 7mo ago
How did they access your Airbnb account?

mfi 7mo ago

I work the email security company xorlab[0], where my colleagues and I did a thorough analysis of real subscription/email bombing waves that we saw at our customers[1]. Here are some interesting additional information from the attacks we analyzed: * Email bombing as a service is a thing, where you can buy 10,000 credits for $10 and easily bomb target inboxes with over 2000 emails per hour. * Most all email bombing attacks starts in the morning, between 8-10. * Most common day of attack is Friday [0] https://www.xorlab.com/en/ https://www.xorlab.com/en/ [1] https://www.xorlab.com/en/blog/from-chaos-to-control-insights-from-24-email-bombing-waves https://www.xorlab.com/en/blog/from-chaos-to-control-insight...

paaradise 7mo ago

> that meant each victim received three emails from us in under a minute: > Verify your email address > Welcome to Suga > Reset your password > Three emails they never asked for, from a product they may never have heard of. We were just one of potentially hundreds of sites being hit at the same time. @homelessdino Why would you send welcome and reset to some victim that DID NOT verify?

simonkagedal 7mo ago
This is being addressed in the article. The service no longer does this, and he apologizes.

CrzyLngPwd 7mo ago

We experienced a similar thing; Thousands of new accounts were being created over a short period, but it was Amazon SES sending us a warning about complaint numbers that woke us up to it. We added a captcha and used a disposable email checking service to get rid of it.

s99850 7mo ago

[flagged]

shreyssh 7mo ago

[flagged]

shreyssh 7mo ago

[flagged]

avian 7mo ago

> The goal [...] to flood the victim’s inbox with so much noise that they can’t find the emails that actually matter. > While the victim is drowning [...] the attacker is doing something else. In the past months some personal mail accounts on a mail server I administer were victim of something that looked similar to what's described here. Hundreds of mails apparently originating from various (legit-looking) random public web services, support requests, issue trackers, web contact forms etc. For example, a good part of them was from Virginia Department of Motor Vehicles (as in something like "thank you for filing a document #123 with us"). To make things even weirder, they were not sent directly to the address, but according to message headers were bounced through Google Groups (each time I checked the relevant group was already deleted). So as far as I can tell it was not the mail address hosted on my server that was being entered into those websites. No phishing links, no attached malware, no short advertisements snuck into a text field etc. Just a huge amount of automated replies from "noreply@" legit entities. I've seen several of these attacks and spent some time investigating them. To my knowledge these were not associated with any other malicious activity, like the author of the article mentions. If anything they were just a denial-of-service attack on a mail box (as in, making the human user trawl through garbage, the mail volume was far from saturating the server itself). What exactly would be a motivation for that I can't tell, except making the life of a small mail server admin even harder than it already is.

motbus3 7mo ago

I know this is ain't new But I am tired of people turning everything into weapons When I started working I wanted to see things being built and evolve Now, every mofo just wants a grant to ---- innocent kids in school.

aservus 7mo ago

The irony is that the services most vulnerable to this are the ones that collect the most email/data in the first place. Minimal data collection is the best mitigation.

thisisnow 7mo ago

Interesting, until it turned into an ad for Cloudflare, it spreads like plague on the internet, slowing everyday down, forcing JS and trying to pull every single datapoint from your browser. Is this really the _only_ solution?

z3t4 7mo ago

Could ask new users to send an email on a generated temp adress before sending the confirm e-mail. I do think e-mail should be not only opt-in, but also optional!

jiehong 7mo ago

I think it’s time to stop using emails in general for all of that. What’s the alternative, though? What if each service generates a link to a uuid url where all new message will be displayed? The user can rss subscribe to that. So the user doesn’t receives anything.

SophieVeldman 7mo ago

[flagged]

dgellow 7mo ago

Oh that’s interesting. I think that matches perfectly with an experience I had with a micro saas I run. I first thought people discovered it organically because it started with just a few signups throughout the weekend, then eventually escalated to multiple an hour. None of the accounts were active but email addresses didn’t look too odd and they weren’t bouncing. I eventually added a captcha that seems to have been effective, but that was a surprising experience because there is nothing you can use that saas for anything nefarious as far as I’m aware

croemer 7mo ago

Incidentally, email bombing was likely used in the axios attack to bury some important security notifications: https://github.com/axios/axios/discussions/10612 https://github.com/axios/axios/discussions/10612

jeninho 7mo ago

[dead]

petercooper 7mo ago

As a newsletter company, we've dealt with this for over a decade now since we do the right thing and do double opt-in which involves sending the subscriber an email on signup. Until a few years ago, IP reputation was a good defence against this. The bad traffic almost entirely came from IP addresses in certain countries or from datacenter IPs we could block. Nowadays, that doesn't work due to the prevalence of VPNs, so many legitimate users appear to come from low reputation IPs. Turnstile is a reasonable solution in its normal form, though the 'invisible' option still lets a lot of them through. Another thing that works, surprisingly, is looking for "webdriver" usage. Despite being easy to strip out webdriver fingerprints, we find that the majority of automated attempts do not bother to do this. Adding more steps, honeypots (with an immediate short term IP ban), etc. also have an impact. It becomes a game of piling up numerous defences in a sort of "Swiss cheese model".

aftbit 7mo ago
That's a fun cobra effect. Age verification ("intended" to make children safer online, if you take the most charitable view) forces more and more people to use VPNs, which overall degrades the value of IP reputation as a signal, forcing providers to accept less reputable IPs because real customers come from them, which means that providers are more vulnerable to attacks that can be used to target children.
- observationist 7mo ago
  The point isn't protection from attacks that target children, it's gatekeeping content to keep it away from children. Providers are more vulnerable to attacks, overall, because of that gatekeeping, because of ht inevitable use of tools like VPNs and proxies to bypass the mechanisms being used. This sort of anti-anonymity is specifically and precisely targeted at decreasing the security of individuals, subjecting them to surveillance and control by the state. It has nothing to do with "protecting the children" and never did. The four horsemen of the infocalypse are always about power grabs, they're never about actually protecting citizens, or children, or securing a country or region.

razkaplan 7mo ago

[flagged]

usernamed7 7mo ago
as expected, this is slop

perching_aix 7mo ago

I'm not sure this is on the email address form providing service's side to combat. This is an inherent issue to email. Email should evolve finally, or disappear.

rglullis 7mo ago

So that explains the handful of random sign-ups I am getting on Communick. The pattern fits exactly what I am seeing as well (3-4 signups in an hour, weird usernames and gmail/hotmail addresses with lots of "." that are usually ignored. At least on my case the mitigation comes with my obsession in not collecting any unnecessary data. Email address are optional and only used if you are already a paying subscriber. Maybe I should just remove it from the sign-up form altogether and use it as a honeypot.

tmarice 7mo ago

I don't really understand the captcha hate, it's table stakes for any public-facing form. You need to pick a point on the "Ease of signup" vs. "Security" curve, and email signup + captcha seems to be the sweet spot. I haven't seen any proof that the big ones (Google, CF) can be easily and automatically bypassed, and would love to learn more if someone has evidence to the contrary.

LEDThereBeLight 7mo ago
Anyone who’s trying to make money through stuff like this (versus just experimenting) is using one of the many paid captcha-solving APIs, which cost a cent or two per solved captcha.
withinboredom 7mo ago
My blog does a proof-of-work before submission (withinboredom.info) in your browser. It'll use a fair bit of cpu power, but should only take a few seconds to complete. For an attacker... that's quite slow and self-limiting.
- eduction 7mo ago
  I did Ctrl-F on "proof-of-work" in this thread to see if anyone had tried this, you seem to be the only one. Seems like a good precaution before sending even a verification email. Did you have to roll your own or was there some proof of work library you were able to use? Update: Ah, found the code - https://withinboredom.info/posts/how-this-blog-actually-works/#1-subscribing-with-proof-of-work-rate-limiting https://withinboredom.info/posts/how-this-blog-actually-work...

gadders 7mo ago

I had this happen to me at the weekend. Someone bought a train ticket using my debit card and then (I assume) in an attempt to hide the copy of the ticket that was emailed to me, I was subscription bombed at the same time.

arafeq 7mo ago

[flagged]

veyh 7mo ago

Oh, that actually explains a lot. I used to offer a 7-day free trial for one of my apps that you could sign up for with an email, and the vast majority of the licenses were never used. The app wasn't even downloaded that many times. I stopped offering the trial since I figured it was not useful for a relatively cheap (19 EUR) app that has a 30-day money-back guarantee anyway. (It can also be used for 15 mins without a license, but requires a restart after that.)

halapro 7mo ago

Back in my day people would sign you up to porn newsletters and those would not ask twice.

frankest 7mo ago

I has gone down recently (or they switched to other sites), but it was coming from EU VPN addresses at first before they got lazy and used mostly Russian IPs.

patrickRyu 7mo ago

[flagged]

tantalor 7mo ago

Mitigating this is kind of pointless, because so many sites are vulnerable to this. I got subscription bombed from about a dozen .gov sites a while back. Healthcare.gov, Social Security Administration, WTC Health Program, FDA, National Institute of Mental Health, Medicare.gov. It's very easy for attackers to do this. Putting in effort to solve this for one site, and expecting any impact, is like trying to empty the ocean with a teaspoon.

alsetmusic 7mo ago
You mitigate because you want to be responsible and not contribute to a problem. One person has to be the first to do something better before it can become a thing that is a best practice throughout an entire industry.
- tantalor 7mo ago
  Like I said, it's pointless.
  - alsetmusic 7mo ago
    Oh, sorry. I didn’t realize you were commenting from a position of selfishness. For people who want to put in a little more effort in hope of inspiring others to do the same and maybe eventually encourage positive change, it’s great.

pagecalm 7mo ago

Honestly just don't send anything past the verification email until the address is confirmed. A lot of the other fixes here are working around what's really just auth libraries trusting the address on signup. Feels like that's the thing worth fixing first.

fyrn_ 7mo ago

The attack doesn't work on hey mail, since new senders have to be accepted before they go the inbox. Presumably Google or whatever is already whitelisted and just goes through

xkbear89 7mo ago

[flagged]