Microsoft shipped its 24th security bulletin for 2005 on Tuesday with a fix for a well-known—and potentially dangerous—flaw in the Windows 2000 operating system.
The patch arrives three weeks after the public release of a proof-of-concept exploit by Israels GreyMagic Software and carries a maximum severity rating of "important."
According to Microsoft Corp.s MS05-024 bulletin, the vulnerability could allow attackers to take "complete control of an affected system."
GreyMagics original alert pinpointed the bug in Windows Explorer, the default utility that lets users navigate through the Windows file system.
GreyMagic discovered that the preview pane, or Web view, in Windows Explorer could be targeted to launch malicious code on machines running Windows 2000 Professional, Windows 2000 Server and Windows 2000 Advanced Server.
Microsoft said its Windows 98, Windows 98 SE (Second Edition) and Windows ME (Millennium Edition) operating systems were also affected, but because the bug isnt rated "critical," patches were not released.
Microsoft does not publicly release noncritical security fixes for those operating systems because mainstream lifecycle support has expired.
Oliver Friedrichs, senior manager at Symantec Security Response, urged Windows 2000 users to take proactive steps to apply the newest update.
"It would be fairly easy for an attacker to create a malicious document that could compromise a system and circulate this document through e-mail or Web sites," he said.
Friedrichs recommended that users "always avoid opening files from unknown sources" or following links to unverified sites.
Microsoft said users logged in with administrative user rights were at higher risk because a successful attack could allow a malicious hacker to install programs; view, change, or delete data; or create new accounts with full user rights.
"Users whose accounts are configured to have fewer user rights on the system could be less impacted than users who operate with administrative user rights. However, user interaction is required to exploit this vulnerability," Microsoft explained.
As previously reported, Microsoft also unveiled a new security advisories service to provide guidance for security issues that arent classified as vulnerabilities.
The first two advisories provide information for a previously released Windows Media Player update that addressed a spyware-infection scenario and guidance on a Tar Pit Feature provided For Exchange Server 2003 In Windows Server 2003 Service Pack 1.
Microsofts monthly update of the free Malicious Software Removal Tool has been fitted with detections for the Sdbot Trojan family. Win32/Sdbot is a backdoor Trojan that is used by malicious hackers to send commands to hijacked machines.
The tool has undergone a user-interface makeover to add notifications to infected users and to perform full scans if malware is detected during the quick-scan.
The modified tool can also handle the removal of malware from legitimate files that may contain user data and gives users the ability send Microsoft information about generically detected files.