A new strain of Windows virus tries to weed out perverts by identifying all files on PCs that may contain child pornography, then notifies the authorities.

The Noped virus is sent as a VBS (Visual Basic Script) attachment on an email titled: 'Help us all to end illegal child porn now'.

Once the attachment is opened the virus will automatically direct itself to the recipient's address book to send itself on. It then scans the PC's hard drive for any Jpeg pictures with titles that may indicate child pornography.

If the virus locates any such files it will forward samples of them to a list of government agencies.

"We are aware of this worm but as yet have not been alerted to any such [porn]," said a spokesperson for the National Hi-Tech Crime Unit. "On the face of it, it is a very good thing, but it may waste a lot of police time by highlighting files which do not contain illegal content but whose file names match those on the list."

Once the file has distributed the alleged porn it will then display a large text file displaying the international laws on child pornography.

"Even if the virus doesn't work it may deter a few people [from downloading child porn] and if innocent people are affected, if they have nothing to hide then they shouldn't worry," said a spokesperson for the NSPCC.