IT security and control firm Sophos is reminding Twitter users of the importance of ensuring their computer security is up to date following news that Internet celebrity Guy Kawasaki's Twitter account has been used to spread malware that targets both Windows and Mac users.

Hackers posted a message on Kawasaki's Twitter page including a link which claimed to offer a free sex video of Leighton Meester, star of hit TV show 'Gossip Girl'.  Actually clicking on the link takes users to a series of websites which offer to show a tape of the young Hollywood actress.
However, Sophos notes that once users agree to download the video, the webpage will not show the video but will check if you are visiting the site using an Apple Mac or a Windows computer and serve up the relevant piece of malware.
The fact that this tweet claimed to come from Guy Kawasaki is worrying since he has almost 140 000 followers – and, therefore, potential victims.
"By offering the chance to watch a free Leighton Meester sex video, the hackers have probably succeeded in tricking some people into downloading their malware," says Brett Myroff, CEO of regional Sophos distributor, Sophos South Africa. "What's more, many Mac users are still not running anti-malware, and thinking themselves immune to cybercrime, they might have seen no harm in clicking on the link just to see what happened."
Sophos notes that this is the second time this month that hackers have targeted Mac users with the lure of X-rated videos, and advises all computer users to exercise caution when clicking on links on social networking sites like Twitter.