A sample program hit the Internet on Wednesday, showing by example how malicious coders could compromise Windows computers by using a flaw in the handling of a widespread graphics format by Microsoft's software.
Security professionals expect the release of the program to herald a new round of attacks by viruses and Trojan horses incorporating the code to circumvent security on Windows computers that have not been updated. The flaw, in the way Microsoft's software processes JPEG graphics, could allow a program to take control of a victim's computer when the user opens a JPEG file.
"Within days, you'll likely see (attacks) using this code as a basis," said Vincent Weafer, senior director of security response for antivirus-software company Symantec. "This is dangerous in a sense that everyone processes JPEG files to some degree."
The program is the latest example of "exploit code," a sample that shows others how to create attack programs that can take advantage of a particular flaw. Such code preceded the Sasser worm by two days and the MSBlast worm by nine days.
The critical flaw the program exploits has to do with how Microsoft's operating systems and other software process the widely used JPEG image format. Because the software giant's Internet Explorer browser is vulnerable, Windows users could fall prey to an attack just by visiting a Web site that has JPEG images.
The flaw affects various versions of at least a dozen Microsoft software applications and operating systems, including Windows XP, Windows Server 2003, Office XP, Office 2003, Internet Explorer 6 Service Pack 1, Project, Visio, Picture It and Digital Image Pro. The software giant has a full list of the applications in the advisory on its Web site. Windows XP Service Pack 2, which is still being distributed to many customers' computers, is not vulnerable to the flaw.
Users can download the patches from Microsoft's Windows Update and Office Update servers. In addition, the software giant has made available online programs that scan for vulnerable software and patch it.
Symantec and other antivirus companies have released updates for their software to detect graphics being used in attempts to exploit the flaw.