Researchers from Cambridge University and the Massachusetts Institute of Technology (MIT) warned Thursday that Internet calling applications like Skype may provide the ideal disguise for hacker attacks.
The Communications Research Network (CRN) of both renowned universities said no attacks had yet been recognized, but "it is only a matter of time before the technique becomes mainstream."
It had discussed the matter with Voice over Internet Protocol (VoIP) firms like Skype, it said in a statement.
Luxembourg-headquartered Skype, which has been downloaded on 242 million computers around the world and was acquired by eBay last year, was not immediately available to comment. Cambridge University is based in Britain and MIT in the United States.
The CRN's working group on Internet Security said it had discovered that VoIP applications could provide excellent cover for launching denial of service attacks.
In such attacks computers are being hijacked by hackers and turned into so-called "zombies" in order to bombard a Web site or e-mail server with page requests or e-mails. The aim of the attack is that the site or entire network collapses under the pressure.
VoIP programs are popular among consumers because they allow free or ultra-cheap phone calls across the globe.
VoIP cuts a voice conversation into digital bits and hackers can use those data streams for cover, making it almost impossible to trace the source of an attack.
Internet service providers monitor instant messaging traffic which is currently used to trigger attacks.
It is more difficult to trace VoIP traffic which often uses a lot of proprietary software with secret code to make sure that Internet phone calls will not be blocked by Internet service providers or firewalls.
"The loophole could be resolved if VoIP providers were to publish their routing specifications or switch over to open standards," the researchers said.
