Miscreants have turned a YouTube service into a spam relay channel.

YouTube contains a facility that allows users to invite their friends to view videos that they are looking at or have posted. This "Invite Your Friends" system is being used to send out "massive quantities of spam", according to content security outfit Marshall.

The messages, which all come from service@youtube.com, have the same appearance as a legitimate YouTube invite, except they contain pitches for tat such as penis pills and get-rich quick schemes instead of links to online video tat. Both could be considered forms of junk anyway which partly explains why cybercriminals have adopted the tactic.

"Spammers are doing this to defeat spam filters and to lower the recipient’s guard by making it look as though the messages are coming from a perfectly innocuous email address. YouTube’s own Help Centre suggests that you exclude the service@youtube.com email address from spam filtering. The spammers are keenly aware of this," said Bradley Anstis, Marshall’s director of product management.

In August, spammers used a Trojan to automatically generate large numbers of Hotmail and Gmail accounts from which to send spam. The YouTube attack is working on the same principle, according to Marshall.

Sending junk mail from compromised Windows boxes under the control of hackers has become the most popular method to send spam over recent years. But spammers are always looking for new techniques to ensure that their junk mail messages get through. Before botnets entered the scene the use of insecure corporate mail servers that provided "open relays" was widely used by spammers. In some ways the YouTube attack put a Web 2.0 spin on an approach that ceased to be effective, thanks to improved corporate security and block lists. ®