“TDL-4″ Botnet Is Practically Indestructible

A new and improved botnet that has infected more than four million computers is “practically indestructible,” software security experts say.

“TDL-4,” the name for both the bot Trojan that infects PCs and the ensuing collection of compromised computers, is “the most sophisticated threat today,” said Kaspersky Labs researcher Sergey Golovanov in a detailed analysis Monday.

“[TDL-4] is practically indestructible,” Golovanov said and others agree.

“I wouldn’t say it’s perfectly indestructible, but it is pretty much indestructible,” said Joe Stewart, director of malware research at Dell SecureWorks and an internationally-known botnet expert, in an interview today. “It does a very good job of maintaining itself.”

Golovanov and Stewart based their assessments on a variety of TDL-4′s traits, all which make it an extremely tough character to detect, delete, suppress or eradicate.

Because TDL-4 installs its rootkit on the Master Boot Record (MBR), it is invisible to both the operating system and more, importantly, security software designed to sniff out malicious code.

Further,what makes the botnet indestructible is the combination of its advanced encryption and the use of a public peer-to-peer (P2P) network for the instructions issued to the malware by command-and-control (C&C) servers.

“The way peer-to-peer is used for TDL-4 will make it extremely hard to take down this botnet,” said Roel Schouwenberg, senior malware researcher at Kaspersky, ”The TDL guys are doing their utmost not to become the next gang to lose their botnet.”

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