The malware detected by Kaspersky Anti-Virus as TDSS is the most sophisticated threat today. TDSS uses a range of methods to evade signature, heuristic, and proactive detection, and uses encryption to facilitate communication between its bots and the botnet command and control center. TDSS also has a powerful rootkit component, which allows it to conceal the presence of any other types of malware in the system.
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The way in which the new version of TDL works hasn’t changed so much as how it is spread - via affiliates. As before, affiliate programs offer a TDL distribution client that checks the version of the operating system on a victim machine and then downloads TDL-4 to the computer.

Affiliates receive between $20 to $200 for every 1,000 installations of TDL, depending on the location of the victim computer. Affiliates can use any installation method they choose. Most often, TDL is planted on adult content sites, bootleg websites, and video and file storage services.
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Just like Sinowal, TDL-4 is a bootkit, which means that it infects the MBR in order to launch itself, thus ensuring that malicious code will run prior to operating system start. This is a classic method used by downloaders which ensures a longer malware lifecycle and makes it less visible to most security programs.

TDL nimbly hides both itself and the malicious programs that it downloads from antivirus products. To prevent other malicious programs not associated with TDL from attracting the attention of users of the infected machine, TDL-4 can now delete them. Not all of them, of course, just the most common.
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One of the most outstanding new features of TDL-4 is the kad.dll module, which allows the TDSS botnet to access the Kad network. So what do the cybercriminals want with a publicly accessible file exchange network?

We have known about botnets controlled via P2P for some time now, although until now, these were closed protocol connections created by the cybercriminals themselves. In contrast, TDSS uses a public P2P network in order to transmit commands to all infected computers in the botnet.