4 ms·

VoIP won, at the cost of making mostly everyone just ignore all calls now. The calls are incredibly cheap, so 99.997% of calls the average person gets are VoIP

by nikanj 4y ago

VoIP won, at the cost of making mostly everyone just ignore all calls now. The calls are incredibly cheap, so 99.997% of calls the average person gets are VoIP spam.

LinuxBender 4y ago
Adding to this, the last time it was mentioned here I started watching SIP SRV requests on my DNS servers and sure enough it's non stop. I added bogus records and the bots follow them and try to connect. Now I just need to find a medium interaction SIP honeypot / tarpit. I already do this for SMTP. Perhaps there is a way to run Asterisk in some debugging mode to accept anything, never tried.
- yokem55 4y ago
  There are kamailio setups that just respond to every request with a 200 OK, and then log the source in a db. If you want to get fancy with that you could make it reply to invites with 100 Trying and make them wait a bit for whatever timout they want to have. The problem with tarpiting them though is that it is hard to make them tie up more resources then you spend on it. SMTP can abuse tcp to send replies 1 charachter at a time with long delays between each one. SIP TCP doesn't really have the same capability.
  - LinuxBender 4y ago
    I will give Kamailio a shot. It's at least a starting point so I can get some stats on what a majority of them are doing. It seems Kamailio is already in the Alpine Linux repository so that saves me a step.
  - jeroenhd 4y ago
    With SIP you'll probably need to exploit SIP directly, not the underlying protocol. Things like redirect loops may confuse callers. With a bit of luck you can redirect the caller to call sip:defaultspamuser@localhost so it calls itself, or redirect it to another bot you've detected to make the spammers bother each other.
jeroenhd 4y ago
Funnily enough, this problem is very localized. I've received two or three spam calls in my life, all of them foreign numbers hanging up immediately and hoping I'd call them back so they can charge excessive service fees. Call spam is more of a cultural problem than a technological one, the relevant culture being the government's and the telcos' culture of not giving a damn about people when there's money or bribes/"campaign investments" to be made. Compare, for instance, your average messaging app: WhatsApp/Facetime/Signal/Telegram offer calls for no cost at all, yet spam is almost entirely non-existent there, because these companies have an interest in keeping their customers happy.
- noAnswer 4y ago
  I think you are right. My parents German landline received way more spam calls in the 1990s than now. Now it's almost non existence, despite the number being unchanged since 40 years and in public telephone books. - Unsolicited commercial calls got outlawed. - Giving your ok to being called for ad-stuff can't be combined with other oks. - Foreign telecom networks can't pretend to have a German number. Local providers are required to strip the number, making the call look less trustworthy. - Having the minute price being said when calling an expensive number.
- WarOnPrivacy 4y ago
  > Funnily enough, this problem is very localized. I've received two or three spam calls in my life Can you elaborate on your local? I can't imagine anyone in the US having this experience. My US number is in a low-density area code and changes every other month; I still need to use a call screening app.
  - jeroenhd 4y ago
    I'm in the Netherlands, but other European countries seem to report very similar things. Business phone numbers, especially mobile numbers, get attacked by scammers constantly, but even those don't always bad enough to warrant the need for a USA-level call filter. Plenty of other scams (for example, targeting the elderly through their landlines or over WhatsApp) but non-business numbers get very few scam phone calls.
dboreham 4y ago
An extra "overlay signaling network" has been added: nobody answers a phone call unless they received an email/signal/SMS/slack to let them know it is coming.
icedchai 4y ago
I get about 4 or 5 "probably a scam" calls a day. It's incredible. I used to bait the scammers and waste their time, but I think they put me on their shit list so I get even more calls now.

by nikanj 4y ago

VoIP won, at the cost of making mostly everyone just ignore all calls now. The calls are incredibly cheap, so 99.997% of calls the average person gets are VoIP spam.

LinuxBender 4y ago

Adding to this, the last time it was mentioned here I started watching SIP SRV requests on my DNS servers and sure enough it's non stop. I added bogus records and the bots follow them and try to connect. Now I just need to find a medium interaction SIP honeypot / tarpit. I already do this for SMTP. Perhaps there is a way to run Asterisk in some debugging mode to accept anything, never tried.

yokem55 4y ago
There are kamailio setups that just respond to every request with a 200 OK, and then log the source in a db. If you want to get fancy with that you could make it reply to invites with 100 Trying and make them wait a bit for whatever timout they want to have. The problem with tarpiting them though is that it is hard to make them tie up more resources then you spend on it. SMTP can abuse tcp to send replies 1 charachter at a time with long delays between each one. SIP TCP doesn't really have the same capability.
- LinuxBender 4y ago
  I will give Kamailio a shot. It's at least a starting point so I can get some stats on what a majority of them are doing. It seems Kamailio is already in the Alpine Linux repository so that saves me a step.
- jeroenhd 4y ago
  With SIP you'll probably need to exploit SIP directly, not the underlying protocol. Things like redirect loops may confuse callers. With a bit of luck you can redirect the caller to call sip:defaultspamuser@localhost so it calls itself, or redirect it to another bot you've detected to make the spammers bother each other.

jeroenhd 4y ago

Funnily enough, this problem is very localized. I've received two or three spam calls in my life, all of them foreign numbers hanging up immediately and hoping I'd call them back so they can charge excessive service fees. Call spam is more of a cultural problem than a technological one, the relevant culture being the government's and the telcos' culture of not giving a damn about people when there's money or bribes/"campaign investments" to be made. Compare, for instance, your average messaging app: WhatsApp/Facetime/Signal/Telegram offer calls for no cost at all, yet spam is almost entirely non-existent there, because these companies have an interest in keeping their customers happy.

noAnswer 4y ago
I think you are right. My parents German landline received way more spam calls in the 1990s than now. Now it's almost non existence, despite the number being unchanged since 40 years and in public telephone books. - Unsolicited commercial calls got outlawed. - Giving your ok to being called for ad-stuff can't be combined with other oks. - Foreign telecom networks can't pretend to have a German number. Local providers are required to strip the number, making the call look less trustworthy. - Having the minute price being said when calling an expensive number.
WarOnPrivacy 4y ago
> Funnily enough, this problem is very localized. I've received two or three spam calls in my life Can you elaborate on your local? I can't imagine anyone in the US having this experience. My US number is in a low-density area code and changes every other month; I still need to use a call screening app.
- jeroenhd 4y ago
  I'm in the Netherlands, but other European countries seem to report very similar things. Business phone numbers, especially mobile numbers, get attacked by scammers constantly, but even those don't always bad enough to warrant the need for a USA-level call filter. Plenty of other scams (for example, targeting the elderly through their landlines or over WhatsApp) but non-business numbers get very few scam phone calls.

dboreham 4y ago

An extra "overlay signaling network" has been added: nobody answers a phone call unless they received an email/signal/SMS/slack to let them know it is coming.

icedchai 4y ago

I get about 4 or 5 "probably a scam" calls a day. It's incredible. I used to bait the scammers and waste their time, but I think they put me on their shit list so I get even more calls now.