Hundreds of reports are coming in of a new Trojan spreading around the globe by posing as home made pornographic pictures.

The email arrives with the subject line 'Re[2] Mary' and starts: "Hello my dear Mary, I have been thinking about you all night. I would like to apologize for the other night ..."

But once the 'Private.zip' attachment is opened, a Trojan called Sysbug copies a file called sysdeb32.exe to the hard drive and alters the registry settings to ensure that it is activated on start-up.

The Trojan allows remote access to the PC, but is not a virus as it does not mail itself on to other computers. The original email was spammed out worldwide last night.

"The author thinks that most men are dogs who'll look at anything for kicks," said Graham Cluley of antivirus company Sophos.

"Once activated the Trojan will allow remote access to a computer, and maybe the writer thinks the type of person who opens the attachment would have other images he might like to look at."