A previously unknown flaw within Microsoft Word 2000 running on Windows 2000 systems has been targeted with a new zero-day attack. Several antivirus companies have reported seeing a new Trojan horse which, when executed, downloads another Trojan, and in turn downloads yet another Trojan onto the vulnerable system. The catch: a user on a Windows 2000 system running Word 2000 must first open the infected file. Such a complicated delivery system means that this attack is limited and an unlikely candidate for a widespread worm attack in the near future. Microsoft has not commented on whether it intends to patch the new flaw within Word 2000. News.com has more details.