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US Report: Visual Basic holes open for e-mail viruses

Anti-virus researchers have identified a class of viruses, called HTML viruses, which hide out in Web pages or e-mail and attack users when they view the content.
Written by ZDNet Staff, Contributor

"Just the fact that your mail program shows e-mail in a window (could) spread the virus to your system," said Igor Grebert, senior researcher at anti-virus maker Trend Micro company publicly announced, on Wednesday, efforts to include protection against such viruses in its anti-virus software.

Last week, anti-virus firm Central Command warned of a more isolated virus that affected ActiveX controls in certain cases. Microsoft accused the companies of scare tactics. "We are extremely confident that this is nothing that users should be worried about," said Mike Nichols, Internet Explorer product manager at Microsoft.

Indeed, at present, HTML viruses present no danger. Grebert has only encountered what he refers to as "test viruses" that do not have any destructive payload. In addition, while HTML viruses have potential to be nasty, they will have a hard time spreading out of control over the Internet. In order to copy itself to a new Web page, the HTML virus must execute on a machine from which it is allowed to change the page. This essentially means that only Webmasters have the possibility of being "Typhoid Mary." "If you are just a user, you will not infect other people's Web pages," said Grebert.

Still, whoever they are, the virus writers have been busy. In the past two weeks, Trend Micro has tallied no less than 17 new variants, written in Microsoft VBScript. While none of them could harm users, don't expect the viruses to have their teeth filed for long. Soon, they could cause significant problems for users who get them.

Technically, the viruses resemble normal programs. "There is no security in Windows that limits what VBScript can do," said Grebert. "Can it read your files? Yes. Can it format your hard drive? Yes." Essentially a macro virus, the viruses -- written in VBScript -- are embedded in the HTML included in a Web page or e-mail. Users of Windows 98 or more recent versions of Microsoft's (Nasdaq:MSFT) Internet Explorer and Outlook are at risk, according to Trend Micro, since both programs are set up with Microsoft's Windows Scripting Host -- needed to run VBScript.

Microsoft said the problem did not affect Internet Explorer. "As a user you would have to go to a site that was designed to be malicious, and users would have to lower the (default) security," said Microsoft's Nichols. Even when security is lowered, users still are prompted every time a script tries to run, he said, putting only the most ignorant at risk.

Still, Outlook and other e-mail programs that read VBScript will allow the virus to execute, claimed researchers. "The real angle of attack is on HTML e-mail," said Russ Cooper, moderator of NTBugTraq "In that regard, people are wide open to attack." Originally, the threat of e-mail macro viruses was expected to come from Microsoft's combination of Outlook 98 and Windows 98.

At the end of July, Finnish students found holes in Outlook that let viruses spread by e-mail. However, that security hole could only be exploited by luring the user to click on an overlong HTML link. Several experts had predicted that some virus writer would put the two together.

Netscape's (Nasdaq:NSCP) Navigator, which does not support its rival's VBScript, is immune, said Grebert. "Yet, with the new features that Sun is putting into Java to compete with Visual Basic, they may have a similar problem in the future."

In addition, Cooper warns that an HTML virus could be written in JavaScript just as easily as VBScript.

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