Microsoft also issued a "Fix-it" this month that lets IT admins enable Network Level Authentication, which mitigates against certain potential exploit vectors. IT admins can use the Fix-it for added protection as they evaluate MS12-020, which is susceptible to pre-authentication exploit on systems running Remote Desktop Protocol without enabling NLA.

"We understand that our customers need time to evaluate and test all bulletins before applying them. To provide for a bit of scheduling flexibility, we're offering a one-click, no-reboot Fix-it that enables Network-Level Authentication, an effective mitigation for this issue," Angela Gunn of Microsoft's Trustworthy Computing group wrote in a blog post. Gunn said the Fix-it applies to Vista, Server 2008, Windows 7 and Server 2008R2 systems.

Exploits Coming Soon

RDP is a popular method for controlling remote Windows machines, however it is not active by default on standard Windows installations, said Wolfgang Kandek, CTO of Qualys. It needs to be configured and started by the system's owner, which then makes the vulnerability accessible.

"Consequently we expect that only a relatively small percentage of machines will have RDP up and running. The vulnerability itself is accessible through the network , does not require authentication and allows code execution on the targeted machine, a highly prized combination by attackers," Kandek said. "Microsoft has rated its exploitability index as 1, meaning that they expect working exploits to be out in fewer than 30 days."

RDP Recommendations

Kandek is making some clear recommendations for the RDP vulnerability. First, within the week apply the patch on Windows machines that are running the Internet-facing RDP service. According to Kandek, IT admins can scan for port 3389 on the perimeter if there is no updated map.

The patch requires a reboot to become active. IT admins that cannot apply the patch or reboot machines, Kandek said, can configure the firewalls on the machines so that only trusted IPs can access port 3389. He also recommended activating the NLA protocol, which does not have this vulnerability.

"Within the month patch the rest of your systems -- both external and internal," Kandek said. "While the main attack vector is directly through the Internet, it is likely that malware will be equipped with the exploit for the RDP vulnerability, and that it will be used for internal malware propagation."

An Unpleasant Flashback

Tyler Reguly, technical manager of security research and development at nCircle, said Tuesday was a flashback of the bad old Patch Tuesdays. Remote, unauthenticated vulnerability attacks are becoming a rarity these days, with end user and client software being the attack vector of choice recently.

"This brings back a scary, old buzzword though, it's 'wormable.' It's a scary word, but MS12-020 makes it completely possible," Reguly said. "This might be the month to throw the patch rulebook out the window and install this patch faster than your enterprise patch cycle normally allows. It's critical that enterprises apply the MS12-020 patch as quickly as possible."