"Leighton Meester sex tape video free download!"

His message included a link that, after some further clicking, landed Kawasaki's followers on a fake porn site where online criminals try to install a nasty Trojan horse program on victim's computers. And in an interesting twist, the program attacks both Mac and Windows users.

Kawasaki, a well known entrepreneur who is now a a managing director of Garage Technology Ventures, isn't the only person whose account was misused during a new round of Twitter hacking Tuesday, but with nearly 140,000 followers he's the most high-profile. Meester, the star of the TV Show GossipGirl is also said to be the subject of a homemade sex tape that is in circulation.

It's not clear how hackers managed to gain access to Kawasaki's account -- security experts say that he and others may have fallen victim to earlier Twitter phishing attacks, where attackers tried to trick victims into logging into fake Twitter sits in hopes of stealing their login credentials.

Other hacked accounts are being used to to promote pornographic Web sites. Victims include an , an , and a (note, some of these Twitter pages still include pornographic and possibly malicious links)