Botnet Herders Can Hide Behind VoIP

Internet telephone applications like Skype and Vonage could become hacker hideouts, a group of technologists and academics funded by MIT and Cambridge University said Thursday.

According to the Communications Research Network (CRN), voice-over-Internet (VoIP) software could give perfect cover for launching denial-of-service (DoS) attacks.

Jon Crowcroft, a Cambridge professor and the lead CRN researcher on the problem, noted that if botnet "herders," the term given to attackers who control large numbers of bot-infected PCs, turn to VoIP applications for command and control, security experts might find it impossible to trace back an attack to the perpetrator.

Current practice by most botnet herders is to issue commands to their armies of "zombie" machines over IRC (Internet Relay Chat) channels, or less frequently, via instant messaging (IM).

Crowcroft argued that attackers could use VoIP's ability to dial in and out of its overlays to make their tracks impossible to trace. In addition, proprietary protocols -- in some cases used by VoIP software to ensure ISPs can't block their applications -- make it tough for providers to track DoS attacks. Ditto for the encryption these applications offer and their peer-to-peer approach to routing packets."While these security measures are in many ways positive," said Crowcroft in a statement, "they would add up to a serious headache if someone were to use a VoIP overlay as a control tool for attacks.

"It would be much harder to find affected computers and almost impossible to trace the criminals behind the operation."

The CRN recommended that VoIP providers publish their routing specs or switch to open standards so that law enforcement and ISPs can properly track misuse of the technology.

"Criminal activity on the Internet should be a notifiable event," said David Cleevely, CRN chairman, in a separate statement. "It's important to remember that there are more of us good guys than there are bad guys. The more we share information between us, the more we stay ahead of the game."

No such VoIP-directed DoS attacks have been seen in the wild, noted Crowcroft, but Internet telephony has been cited as a potential security risk by others, and some applications, notably Skype, have had to be patched against more mundane vulnerabilities.In late 2004, for instance, Symantec predicted that VoIP would become a security headache in 2005 (it didn't), while in October 2005, Skype had to issue fixes for several bugs that could let attackers hijack PCs.