Security experts warn that an e-mail that offers free pornography but actually contains a virus is spreading all over the Internet. The message, which is entitled "Here you have," contains a link that appears to be a PDF document.

The link actually contains no documents. When clicked, the link will enable the virus to gain access to the user's address book in Outlook and sends itself to every contact contained within.

The virus will also try to disable the computer's security programs through deletion, allowing the worm to remain hidden within the hard drive. The program can also be disseminated through unsecured links between computers that share a network.

A report from BBC News says that companies including AIG, Nasa, Procter & Gamble, Disney and Wells Fargo are all encountering difficulties in preventing the program from spreading through their systems. Employees are said to receive hundreds of copies of the email.

The Web site where the worm was based was closed down. However, other forms of the virus are expected to continue spreading.

Security company Kaspersky said that the program targeted Outlook in the same way as the ILoveYou virus that spread around the world in 2000.