A virus is apparently hitting the popular social networking site Facebook that can infect users' "friends" lists.

The virus sends out an e-mail message from "friends" lists and asks users to download a plug-in to watch a video.

Tech expert Marc Saltzman said the plug-in, which purports to be a new Flash player, is actually a virus.

Saltzman said Facebook users might click on the download link because the e-mail message appears to be from a friend, whose Facebook photo is attached.

The virus has been noted by several websites, including Saltzman's blog on MSN, tech blog Pocket-lint and by anti-virus software companies Sophos and Symantec.