Microsoft has admitted that some of its Hotmail servers have been infected with the Code Red worm.

But no user email accounts or personal data have been compromised by the attack, Microsoft spokesman Jim Desler said, according to reports. Nevertheless, he promised that Microsoft would conduct an audit of its Hotmail systems to make sure they are safe.

Last month Microsoft's Windows Update site (which among other things gives links to security patches) was also hit by Code Red.

It's not clear if Hotmail was hit by the first Code Red virus or a more virulent strain of the worm, Code Red II, which first appeared last week and has the potential to give attackers system level access to vulnerable machines.

Paul Rogers, a network security analyst at MIS Corporate Defence, said it was unlikely that individual e-mail accounts had been hacked into because of the attack.

Hotmail is configured with a Domain Name Server system that features round-robin load balancing.

This means that every time a user logs in they do so through a different IP address which means, according to Rogers, that it be "difficult to resolve" a url associated with a user's account, making it hard to hack into email accounts.

At the time of writing, Hotmail appears to be up and running and there's nothing on the site giving any indication that an attack has taken place. ®