LONDON, UK: A new e-mail virus that promises access to free sex films is wreaking some of the biggest businesses across the world.

The 'trojan' virus with the subject 'Here you have' is filling inboxes with multiple e-mails after infecting users' address books. In some cases, the virus is bringing down corporate e-mail systems with the sheer weight of messages, the Daily Mail reported.

Trojans are malicious programmes that hide inside apparently harmless computer files.

The virus arrives as an e-mail with the subject line 'Here you have' and invites the user to click on a link to a PDF file. One of the most common variants promises a link to free 'sex downloads'.

Once the user do so, the virus is downloaded onto his machine and spreads to all the contacts of his e-mail account, sending them the same e-mail in turn.

The worm also tries to shut down any anti-virus software that has been installed.

Firms including Nasa, Comcast, AIG, Disney and Proctor & Gamble have all been affected.

Comcast was forced to shut down its servers Friday after being hit by the virus.

The term 'Here you have virus’ is now one of the most searched for phrases on Google.

One version of the e-mail says, 'Hello: This is the document I told you about, you can find it here' and includes a link to what looks like a PDF.

Another includes the subject 'Just for you' and says 'This is the free download sex movies, you can find it here.'

If you receive the messages, computer security firm McAfee says to delete the message without clicking the link and alert your IT office.

Ram Herkanaidu, security researcher at Moscow headquartered Kaspersky Lab, said that the e-mail closely resembles the 'I love you' virus which caused havoc about 10 years ago.

His firm has now raised their global 'threat' level.

"We've identified an e-mail worm called VBMania. The interesting thing about it is that it uses very old tactics. The worm is so called because it worms itself through your e-mail address book and sends copies of itself out to all your contacts," he said.