Windows
Microsoft on Thursday issued an emergency security update to fix a critical bug in its Windows operating system, which could be exploited by attackers to take over individual and corporate computers. This security update is rated Critical for all supported editions of Microsoft Windows 2000, Windows XP, Windows Server 2003, and rated Important for all supported editions of Windows Vista and Windows Server 2008.
It was for the first time since April 2007 that the software giant has issued a patch outside its schedule of monthly updates. Microsoft said that, the vulnerability could allow remote code execution if an affected system received a specially crafted RPC request. And on Microsoft Windows 2000, Windows XP, and Windows Server 2003 systems, an attacker could exploit this critical vulnerability without authentication to run arbitrary code.
Microsoft recommends that you update your software installation immediately. To know more about the vulnerability and the list of affected and non-affected software, read the official Microsoft Security Bulletin:
http://www.microsoft.com/technet/security/Bulletin/MS08-067.mspx