New cross-site scripting attack targets VoIP

Network World - Security researchers have found a way to execute cross-site scripting attacks through VoIP clients, introducing a dangerous new threat almost no one is guarding against, according to vendor Secure Computing Corp.

"It's simply the first time we've seen what's regarded as a Web 2.0 exploit ... being used against VoIP," said Paul Henry, vice president of strategic accounts at Secure Computing. "Few [people], if anyone, bother filtering the VoIP communications happening over SIP because they don't want any performance degradation. Hence, these types of attacks are going to grow."

VoIP desktop clients using the Session Initiation Protocol are the problem area, Henry said. Security researchers discovered the flaw on Oct. 8 and posted a proof-of-concept code on the Internet describing the vulnerability, which they found in a Linksys VoIP product. Henry is not yet aware of the attack being used against real users but said it's just a matter of time now that the proof of concept is out there.

"It's the tip of the iceberg," Henry said. "I'm very concerned specifically about VoIP because most people who deploy VoIP are doing so in order to save money. ... I'm seeing very little consideration given to security. The field is ripe for picking by the bad guys."

Henry called it irresponsible to publicly disclose security vulnerabilities without first giving the vendor a chance to create a patch. However, some researchers have said they want to raise awareness about risks with earlier public disclosures, because vendors are slow to respond to vulnerabilities.

This particular cross-site scripting attack could be used to install software on a PC allowing hackers to record and listen to VoIP phone calls, according to Henry. A financially motivated hacker might listen to the conversations of the chief financial officer at a large public company toward the end of a quarter to learn information useful in stock trading.

The same attack could also target mass audiences by installing keyloggers that steal usernames, passwords and other information that could help a criminal raid a bank account, Henry said.

While the reported vulnerability has to do with Linksys, Henry believes it probably spreads across most vendors.

"There are so many new VoIP products hitting the market today. I don't believe they're being developed with security first in mind," he said.

The burden then falls on people deploying a VoIP system to install a product that examines inbound traffic and blocks scripts with malicious intent, according to Henry.

Reprinted with permission from

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