The dreaded Facebook worm Koobface has not only pounded the social networking site for the fifth time in a week, a new variant of the worm has reportedly started navigating across to other similar sites.

Facebook users need to be cautious about the clever 'engineering' that can trick them into setting up the malware. Quite like the past versions of Koobface, the new worm too starts out as a Facebook message - which invariably includes a website link with compelling messages like "a video of you," etc - from a friend.

For viewing the purported video, the users are asked to go in for an update to their Adobe Flash player - and that is actually the malware! The scam catches the users all the more unaware this time around, as the spoofed page with the video appears a lot like the regular YouTube page!

Once the users install the malware, they give it the requisite access to pilfer their logon details from Facebook and other sites, further sending the malware-ridden message to all those listed in the contacts list - thereby giving a thrust to the malware crusade!

Talking about the new Koobface variant, Jamz Yaneza, threat research manager at Trend Micro said that once installed the malware "checks your address book, comments or internal spam. Then the whole process starts all over again!"