Microsoft last week revealed its new operating system (OS) is vulnerable malicious hacking attacks designed to extend user privileges.

Microsoft is investigating a security vulnerability which affects Vista, its newly launched operating system.

Mike Reavey, operations manager at Microsoft’s Security Response Centre revealed last Friday the company was investigating the flaw, which can affect different versions of Windows.

In his blog, Reavey said proof-of-concept code exploiting the vulnerability had been posted online. But he added that Microsoft isn't yet aware of any malware existing to take advantage of it.

Reavey said initial indications were that, in order for the attack to be successful, the attacker must already have authenticated access to the target system.