Spammers are exploiting YouTube to send out huge quantities of spam.

Content filtering firm Marshall reported that spammers have set up a large number of bogus YouTube accounts to forward on spam using the 'Invite Your Friends' feature of the site.

"YouTube users have a facility where they can invite their friends to view videos that they are looking at or have posted," said Bradley Anstis, director of product management at Marshall.

"This effectively allows them to email any address from their YouTube account, and this is the functionality that the spammers are exploiting."

The technique is more effective than standard methods because spam filters generally recognise YouTube as a trusted address and let the emails through.