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Glad this is at the top. The linked Reddit thread demonstrates a common but fundamental misunderstanding of SIP. Port 5060 is used for call control and is very
by kkielhofner 4y ago
Glad this is at the top. The linked Reddit thread demonstrates a common but fundamental misunderstanding of SIP.
Port 5060 is used for call control and is very low traffic. At most you may have timed OPTIONS messages but a “standard” SIP deployment is at most a handful of (small) packets per second per call setup and tear down with occasional REGISTER messages on an interval measured in seconds. Very low traffic and very low bandwidth. Obviously with more devices you get multiples of these numbers but still very low. 15 kbps is a pretty significant amount of SIP traffic.
This is most likely targeting VoIP abuse from tools like sipvicious. In a nutshell they scan the internet looking for open SIP ports. They then try to brute force credentials to place calls.
Why? Toll fraud. The scam works like this:
1) Setup an international toll charge number in some country. Let’s say it charges $5/min. For those that don’t know calls to these numbers get charged to the person placing the call from their phone company and end up on their phone bill with the amount getting paid out (less a cut) to the operator of the number.
2) Compromise a bunch of random exposed SIP implementations on the internet.
3) Place calls to your (or a partners) toll number.
4) Get paid from the toll charges.
5) Some time later the owner of the compromised system gets a huge bill depending on fraud detection systems at the carrier, how fast you could pump calls, etc.
It’s gotten so bad many VoIP providers block international calls by default and now (apparently) might be blocking 5060 traffic in some way.
This isn’t that different to what’s happened with SMTP over the years. To combat spam many last mile ISPs started blocking outbound TCP port 25 so compromised machines couldn’t directly send spam. This is where port 465/587 for SMTP “submission” came from.
- deleted 4y ago[deleted]
- TheWoodsy 4y agoPerfect example of one of the many SIP abuses I have personally seen here in Australia. Don't get me started on the bajillion 3G+ modems here with default passwords.
- devwastaken 4y agoNot the ISP's responsibility.
- robocat 4y agoHowever the ISP will get blamed by some victims.
- kkielhofner 4y agoI’d argue that a reasonable network limitation with a minimal blast ratio is responsible. For example, I use SIP over 5060 on Spectrum without issue. Not having their network used by bots to inflict untold financial damage is being responsible. Would you argue that implementation of BCP38 to cut down on bots used in DDoS attacks is “not the ISP’s responsibility”? Plus, they get the abuse reports from the victims and I’m certain this traffic is a ToS violation for their customers and certainly against the CFAA and numerous other laws for the resulting theft and fraud it causes.
- kevin_thibedeau 4y agoBlock by default is fine but customers should be empowered to disable them if they need the IP service they're paying for.
- unethical_ban 4y agoNah, just like port 25 outbound being blocked is shitty. How can we have a decentralized net when consumer ISPs make people call in or beg to have full network access? Yes, do some flood detection, but the problem is that the SIP provider should be, as another commenter put, block international calls or otherwise detect/reject calls to toll systems. Who the heck uses toll numbers anymore anyway?
- kkielhofner 4y ago"People" here being the 0.001% of the population that's interested in and capable of responsibly hosting anything. As others have noted I'm perfectly fine with someone having to make a phone call, go to a web UI, whatever to click a box with a scary warning (and potentially agree to additional terms) when they want to open their connection up. Spectrum has 32 million customers and blocking SMTP, netbios, RDP, rate limiting SIP, etc are reasonable defaults. The alternative (today) is the literally millions of compromised PCs, IoT devices, etc that inflict incredible amounts of damage and make even more decentralizing services like CloudFlare essentially a necessity to make sure whatever you're hosting can deal with the possibility of terabits of traffic from a botnet showing up at any second (or SPAM, or VoIP fraud, etc, etc). As it stands now we have both and there is still an incredible amount of trash traffic - see other comments in this thread about people trying to host their own Asterisk instance and having it use 100% CPU just processing all of the malicious trash traffic showing up. I mentioned blocking international calls by default in another comment. So now you need to contact your provider just to call someone in another country? Unfortunately, yes, that has been the case for many VoIP enabled systems for almost a decade now. In NANPA (North American Numbering Plan) the international call prefix is 011. This is trivial to put behind a flag. However, after that detecting toll numbers is much more difficult because you're dealing with the entire world at that point and the numbering schemes, etc for toll numbers are all over the place. Additionally, in many countries there isn't any rhyme or reason to their toll numbering and unscrupulous network operators and jurisdictions that don't have a functioning legal system capitalize on all of this. It's been a while but I even remember some destinations in the caribbean taking advantage of having a +1 country code so not even the "international" call prefix block works in that case. In my past life I was the CTO for a VoIP service provider with hundreds of thousands of business VoIP systems. This issue is very vast and complex while looking from the outside like yet another HN "Why don't you just do X" or "I could solve that in a weekend".
- tinus_hn 4y agoThe real abuse of course is $5 a minute toll line. The ability to rack up that kind of charge should be opt-in, there’s basically no legitimate use case.