A third version of Downadup has been identified by Symantec, which says the new variant gives infected machines more powerful instructions to disable anti-virus software and analysis tools, among other actions.
W32.Downadup.C is a modular component for machines currently infected with Downadup. This variant of Downadup, also called Conficker, is not attempting to self-replicate and appears to behave more like a Trojan than a worm, says Vincent Weafer, vice president of Symantec Security Response.
"Think of it as an updated module that's more aggressive, more robust in defending itself," Weafer says.
The W32 Downadup.C variant was discovered Friday in a Symantec honeypot and is still under investigation. Symantec expects to identify additional capabilities shortly, says Weafer, who adds that Symantec has not yet seen W32.Downadup.C in customer networks directly.
Earlier versions of Downadup did attempt to disable anti-virus software, but the third version represented in the Downadup.C module is designed mainly to provide more protective actions to infected Windows-based machines so they can better defend themselves from anti-virus software and other eradication methods.
"It's more aggressive, it has more services," says Weafer.