In mid-March the security firm Dr. Web published details of a botnet (defined) they were able to shut down affecting players of the classic first-person shooter (FPS) game; Counter-Strike 1.6.
Why should this development be considered significant?
The report made available by Dr. Web showed that at it’s height the botnet resulting from the distribution of the Trojan (defined) Belonard numbered up to 39% of all the available game servers (1951 out of 5000) listed for Counter-strike gamers to choose from.
How were gamers systems infected?
One of the popular services offering servers to play on exploited 2 zero day (defined) remote code execution vulnerabilities within the 1.6 version of the Counter-Strike client to install Trojan Belonard within a gamer’s system. Researchers from Dr. Web found that this game remains very popular and can be played by 20,000 individuals on average at a time.
Counter-Strike can make use of dedicated servers that gamers can choose to connect to. These servers offer reduced lag, greater reliability while some monetised servers offer access to special weapons and protection against bans.
In an example scenario, a gamer might launch the official Steam gaming client. The client automatically will display a list of servers the player can connect to. Those with the lowest (lower is better) ping rate will be displayed at the top of the list. This list will also contain publicly available Valve (the company which created and maintains the Steam client) servers. However, the Trojan Belonard once it has infected a system it re-orders the servers offered to another system (placing them high in the list you see) in order to spread further. You may think you are connecting to a server with a low ping when in fact connecting to a malicious server which then infects your system with the Trojan. It does this by exploiting a remote code execution (defined: the ability for an attacker to remotely carry out any action of their choice on your device) vulnerability within the Counter-Strike client. A more detailed description and diagram is available from Dr. Web’s analysis of this threat. Your system will now contribute to spreading the Trojan by re-ordering the server list we discussed above.
The botnet herder did this in order to make more money since their other more legitimate servers would also be displayed high in the list of servers and those charge a fee for their use.
What happened to this botnet?
Dr. Web was successful in disrupting this botnet by coordinating with the registrar of the reg.ru domain name to shut down the websites used by the Trojan thus protecting new gamers from becoming infected. Furthermore, the domain generation algorithm (DGA)(defined); is being monitored by Dr. Web in order to continue to sinkhole (defined) the domains the malware attempts to use to continue spreading itself.
How can I protect myself from this threat or clean it from my system if I am already infected?
Unfortunately; the only way to prevent this botnet from being re-activated by whoever created it is for the zero-day vulnerabilities within the Counter-Strike client to be patched. Given the age and lack of financial reward to Valve to do this; that is unlikely.
If you suspect or know your system is infected with this malware; update your anti-malware software and run a full system scan. If this does not remove the malware you can use the free version of Malwarebytes to perform a scan and remove the malware. If you suspect any remnants remain you can use the additional anti-malware scanners linked to on this blog to remove them. In this case; RogueKiller, AdwCleaner and PowerEraser would be the most suitable for this malware.