Ramblings & ephemera

How the Storm botnet defeats anti-virus programs

From Lisa Vaas’ “Storm Worm Botnet Lobotomizing Anti-Virus Programs” (eWeek: 24 October 2007):

According to an Oct. 22 posting by Sophos analyst Richard Cohen, the Storm botnet – Sophos calls it Dorf, and its also known as Ecard malware – is dropping files that call a routine that gets Windows to tell it every time a new process is started. The malware checks the process file name against an internal list and kills the ones that match – sometimes. But Storm has taken a new twist: It now would rather leave processes running and just patch entry points of loading processes that might pose a threat to it. Then, when processes such as anti-virus programs run, they simply return a value of 0.

The strategy means that users wont be alarmed by their anti-virus software not running. Even more ominously, the technique is designed to fool NAC (network access control) systems, which bar insecure clients from registering on a network by checking to see whether a client is running anti-virus software and whether its patched.

Its the latest evidence of why Storm is “the scariest and most substantial threat” security researchers have ever seen, he said. Storm is patient, its resilient, its adaptive in that it can defeat anti-virus products in multiple ways (programmatically, it changes its signature every 30 minutes), its invisible because it comes with a rootkit built in and hides at the kernel level, and its clever enough to change every few weeks.

Hence the hush-hush nature of research around Storm. Corman said he can tell us that its now accurately pegged at 6 million, but he cant tell us who came up with the figure, or how. Besides retribution, Storms ability to morph means that those who know how to watch it are jealously guarding their techniques. “None of the researchers wanted me to say anything about it,” Corman said. “They’re afraid of retaliation. They fear that if we disclose their unique means of finding information on Storm,” the botnet herder will change tactics yet again and the window into Storm will slam shut.

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