Hackers have begun exploiting the new "Shellshock" computer bug, using worm viruses to scan for vulnerable systems and then infect them, researchers warned on Thursday. Kaspersky Lab reported that a computer worm has begun infecting computers by exploiting "Shellshock." The malicious software can take control of an infected machine, launch denial-of-service attacks to disrupt websites, and also scan for other vulnerable devices, including routers, said Kaspersky researcher David Jacoby.

"Shellshock" may not affect as many systems as "Heartbleed" - which affected encryption software used in about two-thirds of all web servers - but has the potential to wreak more havoc because it enables hackers to gain complete control of an infected machine, which lets them destroy data, shut down networks or launch attacks on websites.

Amazon.com and Google have released bulletins to advise web services customers how to protect themselves from the new cyber threat.

Linux makers has also released patches to protect against attacks on Wednesday.

Apple on Firday said the vast majority of Mac computer users are not at risk from the "Shellshock" computer bug, which security experts have warned affect operating systems, including Mac's OS X.

"Shellshock" is a vulnerability in Bash, a piece of software packaged with Mac OS X, which is based on the Unix operating system. The bug does not appear to affect Apple's iOS, which is used on the iPhone and iPad, or machines running Microsoft's Windows software.