On Dec. 27, 2005 a Windows Metafile (.WMF) flaw was discovered affecting fully patched versions of XP and Windows 2003 Web Server. Simply by viewing an image on a web site or in an email or sent via instant messenger, code can be injected and run on the target computer. The vulnerability was in the Windows Graphics Rendering Engine which handles WMF files, so all programs such as Internet Explorer, Outlook and Windows Picture and Fax viewer which process this type of file were affected.
Within hours, hundred of sites start to take advantage of the vulnerability to distribute malware. Four days later, the first Internet messenger worm exploiting the .wmf vulnerability was found. Six days later, Panda Software discovers WMFMaker, an easy-to-use tool which allows anyone to easily create a malicious WMF file which exploits the vulnerability.
While it took mere hours for cybercriminals to take advantage of the vulnerability, it took Microsoft nine days to release an out-of-cycle patch to fix the vulnerability. For nine entire days the general public was left with no valid defenses.
The WMF Flaw was a security nightmare and a cybercriminal dream.It was a vulnerability which (a) affected the large majority of Windows computers (b) was easy to exploit as the victim simply had to view an image contained on a web site or in an email, and (c) was a true zero-day with no patch available for nine days. During those nine days, the majority of the general population had no idea how vulnerable they were.