Experts are warning of new emails being spammed out purporting to offer recipients free access to pornography.

The emails, which contain phrases such as 'hot photos from my birthday', come with a URL which leads the user to a site hosting the Pushu-A Trojan. The user is asked to download a file containing the photos, named 'xxx.exe' or 'foto.exe'.

"As with all messages offering salacious content, the danger is that some people may be so excited about the prospect of viewing the pictures that they'll click before thinking about what might be in the best interests of their PC's health," said Graham Cluley, senior technology consultant at Sophos.

"The email spam campaign has been widely distributed, although thankfully we haven't received many reports of users infected by the Trojan horse.

"Those that visit phoney adult websites risk throwing open their PCs for cyber-criminals to steal information or carry out further online attacks."

In a bizarre twist one of the malware web stores hosts pictures of two US comedians, Lewis Black and Dave Attell. Experts are foxed as to the relevance of the pictures.