The so-called IE Script hole was discovered last month by Bulgarian bug hunter Georgi Guninski. It lets crackers embed malicious Visual Basic code into Microsoft's Access database management software via Internet Explorer.
Victims can be compromised by simply visiting a rogue website or by previewing email containing malicious code, without actually opening any attachments or executing files, according to a security flash issued today by the System Administration, Networking, and Security Institute.
SANS is a nonprofit institute focused on education and research in several information technology areas, including information security.
What makes the hole such a dangerous programming error in Windows software is that it allows crackers to potentially take full control of a victim's computer, according to Alan Paller, director of SANS.
"It allows [a cracker] to do anything I can do as a user of my computer," Paller says. This includes editing files, deleting them, or emailing them to remote destinations without a user's knowledge.
"The problem is really serious," says Ryan Russell, manager of information systems at SecurityFocus, a security firm and moderator of Bugtraq, a popular security bulletin board.
The hole gives crackers "the ability to access the hard drive of the victim. That is about as serious as it gets... It's usually considered the 'game-over' stage," Russell says.
Even so, there have been no reports of incidents in which companies have been compromised by the vulnerability, Russell says.
And despite its serious nature, "it is silly for SANS to call this the 'most dangerous flaw found in Windows workstations,'" says Elias Levy, chief technology officer at SecurityFocus. "There have been flaws in the past that have been worse," Levy says.
For example, the Multipurpose Internet Mail Extension buffer overflow in email clients such as Outlook basically allows crackers to plant malicious code that executes even before a user opens an email message, Levy says. Of more interest is the fact that Microsoft hasn't really implemented a fix but provided only a work-around to the problem, he says.
All users of Windows 95, 98, 2000, and NT 4.0 workstation who have installed Microsoft Access 97 or 2000, while running Internet Explorer 4.0 or higher, are vulnerable to this sort of "total compromise," according to the SANS alert.
Microsoft's work-around is to set an administrator password for Microsoft Access. This will cause Microsoft Access to prompt the user for a password before any Visual Basic for Applications code is executed within an Access database, according to a Microsoft FAQ on the subject.