An old Microsoft vulnerability (announced in April) has now become a bigger problem because of the exploit code that was recently released. All windows systems are vulnerable, so if you're using any Windows system, you should immediately go to Microsoft and download their patches. The vulnerability stems from a failure of the Microsoft Windows kernel to properly handle user-supplied messages. Basically, the kernel allows local users to gain privileges through certain access requests, and a malicious user can exploit this to gain control over the entire system.
Microsoft Windows Kernel CSRSS Local Privilege Escalation Vulnerability (Security Focus) Microsoft Windows CSRSS Local Privileges Escalation (MS05-018, Exploit) (Securiteam.com, September 8, 2005) Microsoft Windows CSRSS Local Privilege Escalation Exploit (MS05-018) Security Focus: Local Privilege Escalation Exploit Microsoft Security Bulletin MS05-018 (Microsoft.com, April 12, 2005)