The problem occurred after Microsoft pushed out an update forlast Thursday night. The updated software identified a Windows registry key set by the Symantec products as belonging to password stealing malicious software known as Bancos, Microsoft and Symantec said in a joint statement Monday.
On detection of the registry keys, Windows AntiSpyware alerted the user and suggested deletion of the keys. "The deletion of these registry keys will cause all versions of the SAV (Symantec AntiVirus) and SCS (Symantec Client Security) software to stop operating correctly," Microsoft and Symantec said in the statement.
The issue affects users of Microsoft's Windows AntiSpyware Beta 1 and various versions of the Symantec security software for corporate users, the companies said. Users of Symantec's Norton-branded consumer products are not affected. Symantec and Microsoft believe only a small number of customers were affected.
Microsoft released a new update for its product on Friday morning to fix the problem. Symantec and Microsoft have prepared a tool to repair installations of Symantec's software that were affected. The tool is available at no charge from Symantec's support department, the companies said.
Though still in beta, Windows AntiSpyware is one of the most popular downloads from Microsoft's Web site and is widely used. The software has been downloaded about 25 million times, according to Microsoft.
This is not the first problem with Windows AntiSpyware. Last year Microsoft, one of MSN's main competitors in the Netherlands, after the software giant's anti-spyware product incorrectly flagged the site as malicious.
Windows AntiSpyware is designed to protect PCs against malicious software, including, which is software that's installed on a system to watch the user's activity without his or her knowledge.
Windows AntiSpyware was renamed Windows Defender last year. The product will bear that name when the second beta version ships, which is expected soon. Windows Defender, the successor to Windows XP due out later this year.