VoIP Attackers – Sometimes They Come Back

In my previous post I briefly touched on information that I had been collecting for over 19 months via what began as VoIP Intrusion Detection system I had whipped up from scratch. The framework for Arkeos began almost three years ago while working here at an ITSP slash managed service provider. One of our services is a “managed VoIP service” similar to Packet8 or Vonage for small to mid-sized business. I lost count of how many PBX’s we maintain nowadays but I will comfortably float this number at around 60’ish. Altogether I have about 1,600 clients mainly small to mid-sized businesses with a couple of Fortune 500’s in the mix. My company also provides SIP trunks and we have about 30-35 VoIP companies who use us as their backbone for their VoIP services. Because of my position in my company (multiple roles), I have great visibility into many different VoIP hardware and software vendors in fact, I can’t think of a VoIP related vendor I haven’t dealt with in the past 5 years. Avaya, Nortel, Mitel, Cisco, Acme Packet, Audiocodes, Allworx, PBXNSIP, Asterisk and the list goes on. Because my “main cup of tea” is security, I began meshing security with VoIP.

Arkeos does a few things: 1) Collects information on bruteforcers 2) Collects information on attackers 3) Records the calls an attacker is trying to send and 4) Mimics a phone so that an attacker thinks they are placing a valid call. When I first scripted it, I had to customize it in accordance to the device it was being deployed on, these were mainly Asterisk based PBX’s. Because I was using different versions of Asterisk, I had to tweak the script almost daily as the columns in Asterisk’s message file was different. For example:

2010-09-25 21:02:48 NOTICE[14155] chan_sip.c: Registration from '"3068" ' failed for '72.55.179.180' - Wrong password
2010-09-25 21:02:50 NOTICE[14155] chan_sip.c: Registration from '"3068"' failed for '72.55.179.180' - Wrong password

These are two different entries to parse with awk. To obtain the first entry, I would use ‘awk {print $10}’ whereas the other would be awk ‘{print $9}’. I initially thought of going with Python, then Perl, but settled on good old fashioned shell scripting. This ensured me that no matter what system I deployed it to, I would be able to use readily available tools on the system without introducing another application. Arkeos in all honesty is a nightmare to look at if you’re a coder, yet completely functional for what it does.

After tweaking it to my needs, I began to see many patterns die and many emerge. Years back, I saw the “fire and forget” method of attacks where you had a bruteforcer compromise an account, then that same bruteforcer fire of as many calls as they could possibly send. Nowadays I see “bruteforce” drive-bys and an attacker come from left field. Without giving up information to potential attackers who may read this, let’s assume I have an account of 5000 with a password of 5000, I’ll see say 10,000 attempts from an address of 10.10.10.10 trying to guess the password, with an attacker from 20.20.20.20 registering to use the account. From more or less November of 2009 through now, I have yet to see a bruteforcer gain an account AND log in at the same time. On the contrary, I don’t see bruteforcers’ addresses on my honeypots anymore.

mysql> use arkeos;
Database changed
mysql> select * from attackers where attacker_address='92.81.245.67';
ZZZZ, 92.81.245.67, Zoiper rev.5324, XXXX, 2010-09-11, 03:16:28
1 row in set (0.00 sec)

mysql> select * from bruteforcers where attacker='92.81.245.67';
Empty set (0.01 sec)

mysql> select * from bruteforcers where start_date='2010-09-11';
Empty set (0.00 sec)

mysql>

NOTE: I modified the output to fit it to page, the exact format of Arkeos and its tables can be seen at: http://infiltrated.net/arkeos-w-mysql.txt and the audio for this call can be heard at http://infiltrated.net/mgz/92-81-245-67-audio.wav)

So why is this information not only important to engineers (be they VoIP, Security, Network or Systems engineers) but also to perhaps law enforcement, the answer is a bit complex so I will try my best to explain my point of view, theory and concept. Imagine that right now I saw a bruteforce attack from say Korea with the account actually being used from say Romania. Romania hoses my machine and costs me say 100,000.00. For the time it would take for an investigation to even take place, get subpoenas in order, go around the world, get those companies to co-operate, at the end of the day, the investigation would likely yield NOTHING. I say this because of the ease of readily available networks and hosts that are likely compromised and used for bruteforcing and attacking. However, this is SOLELY for the bruteforcers. Did I mention the actual attacker is coming from elsewhere?

An attacker is, who I categorize in my writing, someone who has actually tried to place a call through my honeypot. Heck, bruteforcers I can easily block, prior to my honeypot I had created my own Asterisk based IPS capable of blocking bruteforcers in real-time. Attackers I want to believe are a bit more static in the sense that I believe whoever is behind 92.81.245.67 is the culprit who needs to be either arrested or rubber-hosed (depending on your view of justice). So what is relevant for an investigator outside of the attacking IP? For starters, Zoiper is a softphone (for those who don’t already know this) which means this attacker is likely using either a desktop or a laptop. Further, because I’m also tracking the number(s) being called, I gained the following insight:

awk '/407272/{print $1}' /usr/share/arkeos/calls/92.81.245.67/*
0040727246641
01140727246641
00140727246641
901140727246641
90040727246641
90040727246641
90040727246641

What have we here? Intervention is what. Arkeos mimics a telephone so unless an attacker was on the opposite end of the number dialed, how would they know to try 011, 001, 9011, 900 and so on and so forth. Hence the title “Sometimes they come back.” I have seen quite a few attackers coming back week after week from the same addresses sometimes, using the same accounts, trying to call the same number. So where would I look if I were an investigator? Directly at whomever owns that number they’re trying to call, that’s where. I theorize that if one tracked the owner of that number, searched the computers of who owned that number for Zoiper, I’m willing to bet they’re one in the same. Coincidental? Highly unlikely. An IP address, a phone number AND a softphone client ALL coincidentally belonging to one person is more than coincidental.

Anyhow, I have created an online submission form for others to submit attacker data and am trying to figure out a way I can streamline Arkeos to be a “plug and play” script for anyone willing to use it. I will eventually create a database which others who collaborate can update and pull from but I don’t want to run into a thousand emails asking me to “customize” Arkeos. This is the only reason I haven’t made it public. Remember, I made this from scratch and it was tailored to my machines and since all machines differ, I do know that I will receive those emails. To which I have little time to respond to. I try to answer as many emails as I can, but the fact is, I’m all over the place sometimes (literally.)

This entry was posted in SIP, VoIP Attacks in the News, VoIP Security, VoIP Security Research on by .

About J. Oquendo

Security practitioner with a broad range of experience and expertise in networking, security, systems administration/design/engineering, VOIP, application and systems exploitation. Working at a technology (cloud) company that offers various managed security based services. Responsible for Incident Handling, Penetration Testing, Security and Information Risk Assessments, Risks Analysis/Management, Audits and Compliance testing. I no longer publicly disclose the companies I work for – but feel free to ask.

2 thoughts on “VoIP Attackers – Sometimes They Come Back

  1. Ron

    Awesome. I work on a similar work place J., and our systems get scanned as much as 200 times in a day; and most of them are IP’s from China, spoofed or not. Looking forward to this project.

    Reply
  2. shawn mer

    Great write-up J., this is a fine way to share attackers’ tactics and patterns along with your homegrown mitigation strategies. I agree that supporting released code, even scripts, is a PITA, and think you’re moving in the right direction with the explanation and logic in this format. Also, I look forward to a community pooling of this kind of attacker scanning/bruteforce data and the potential insights it can provide.

    Thanks again for sharing :)

    Cheers,
    –scm

    Reply

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