An email currently circulating to customers is a symptom of the virulent MyDoom.O worm that attacked major search engines on Monday.

Internet security company Sophos' Graham Cluley explained: "This mailing is not aiming directly at owners, but is generated by the prevalent MyDoom.O worm.

"The message aims to lure PC users into running the attached file, which infects the machine."

MacFixIt reports the dangerous message reads: "Dear user of We have received reports that your account was used to send a large amount of spam during the last week. Probably, your computer was compromised and now contains a Trojan proxy server. We recommend you to follow our instruction in order to keep your computer safe. Sincerely yours, The team."

Cluley said: "The MyDoom.O worm only runs on Windows machines, not Macs. It's an irritation for Mac users to get the mail, but it can't do them any harm", he said, adding "It's another reason to feel smug about having a Mac."

However, subscribers who access their email using a PC or webmail on a PC should ensure they do not accidentally run the Windows-affecting file.

Sophos recently published its list of top ten viruses, none of which affect Macs.