13 ms·

To me this looks that for ~90% (eyballed) you just need to tell your browser somehow to stay away from any port other than 80 or 443. If some script/link-rel/sr

• toast0 2y ago
  On performance, it depends a bit. If you're running a stateful firewall, those generally don't evaluate firewall rules for established states, and most of your traffic is to established states, so no big deal. If you're not running a stateful firewall, it's not totally unreasonable to skip the firewall for tcp packets with ACK and not SYN, so again no big deal on those. But http/3 is udp, so no shortcuts there. Afaik, most firewalls have a lookup table available, you'd want to use that, rather than 2 million rules. On FreeBSD, ipfw and pf have lookup tables, ipf calls them pools, but it looks like the same thing. A lookup table for IP addresses is pretty fast, even with 2M entries.
  • vladvasiliu 2y ago
    > But http/3 is udp, so no shortcuts there. Usually stateful firewalls create a "state" for UDP connections, so "shortcuts" are still possible. See, for example, pf: https://www.openbsd.org/faq/pf/filter.html#udpstate https://www.openbsd.org/faq/pf/filter.html#udpstate
• schoen 2y ago
  Can anyone explain why malware distributors would prefer (or be somehow forced into using) non-default TCP ports?
  • VoidWhisperer 2y ago
    My (naive) guess is that it makes them slightly less likely to be picked up by scanners like shodan. I'm probably wrong though
    • 9cb14c1ec0 2y ago
      This is a big part of it. There are companies that scan the internet in search of malware, and if you run on a different port it makes the search space so much bigger.
  • sambazi 2y ago
    because the original owner of the box would mind if the application on default port stops working
    • amne 2y ago
      or wonder why weird routes like "/i" or "/bin.sh" are among the top accessed URLs in their monitoring dashboards
  • cess11 2y ago
    The low ports typically require root privileges to map to, and people are more likely to keep track of what runs on them. It's not about Shodan, Shodan will find it. Probably Greynoise too.
  • rvnx 2y ago
    It's because they typically hack web servers, and then they spawn a fresh web server on a random port. Anything below 1024 requires root access, which can be problematic, and 80/443 may already be used.
• wannacboatmovie 2y ago
  Google has been doing a pretty good job at breaking the web on their own via "features" in Chrome, let's not give them any other ideas.
• Glazui 2y ago
  I recently got a pop up in Firefox doing exactly that. I was messing around with my homelab and entered a URL/Port that Firefox deemed suspicious and warned me that “this port is usually not used for web browsing. Are you sure you want to visit that?”
  • amne 2y ago
    I'm hearing more and more nice things about firefox lately. Been on chrome for the last 10 years or so but I might have to switch soon if they break extensions the way the plan to.
• yuliyp 2y ago
  This feels like the wrong conclusion in an adversarial game. Such a heuristic works only because it's not done at any reasonable rate. As soon as it gets applied nontrivially you'll see scammers adapt back to ports 80/443. And you've got a broken browser to boot.
  • amne 2y ago
    I agree that is the likely outcome. It is interesting to me though that they're not concentrated on ports 80/443. There must be a reason why and one answer, from a comment below, could be that boxes hosting this already serve legit http content on those ports. Having this kind of traffic show up in http monitoring tools would make the hack obvious.
    • jdsnape 2y ago
      A lot of stuff is hosted on compromised sites or devices - which are often running some insecure admin interface on an odd port. Very rare in my experience that someone would spin up a new web server on a box they’ve popped.
• plufz 2y ago
  i have little snitch configured to only allow 443 and 80 on my browser and have it display a dialog with accept decline on non-default port requests.
  • sambazi 2y ago
    that's cute
    • plufz 2y ago
      I try to be!
• bauruine 2y ago
  Where do you get those 2 million IPs? The plaintext url list [0] only contains 90k entries and after filtering it to ips only and de duplication it's just 39k. I've just added it to my firewall that does around 160Mbit/s right now using an ipset and the only increase in CPU I can see is a small blip from the ipset restore. And that's just an APU2 with a AMD GX-412TC (1GHz Quad core from 2014) and not a beefy box. [0]: https://urlhaus.abuse.ch/downloads/text/ https://urlhaus.abuse.ch/downloads/text/
  • sambazi 2y ago
    yea, it should not have any performance implications. be aware that blocking stuff in your infrastructure will have hard to diagnose fallout and you're generally better of if you police content on the client (ad-blocker)
• ajsnigrutin 2y ago
  > Also curious what are the performance implications for adding to your firewall about 2 million IPs or maybe a couple 100k if you're brave to do ranges. The problem here is, that the "bad guys" move around, and sooner or later you ban most of the eg. digitaloceans IPs, amazon IPs, azures IPs, etc., and you break conectivity for other, "good" uses.
• accrual 2y ago
  > Also curious what are the performance implications for adding to your firewall about 2 million IPs or maybe a couple 100k if you're brave to do ranges. OpenBSD's pf firewall supports tables of IP address which can be black or whitelisted. From their FAQ: > A table is ideal for holding a large group of addresses as the lookup time on a table holding 50,000 addresses is only slightly more than for one holding 50 addresses. https://www.openbsd.org/faq/pf/tables.html https://www.openbsd.org/faq/pf/tables.html