Microsoft Windows XP at Risk from DoS

Microsoft has released a security advisory over a flaw discovered in Remote Desktop Services, which could allow an attacker to send a specially crafted Remote Desktop Protocol(RDP) request to an affected system.

"Our investigation has determined that this is limited to a denial of service, and therefore an attacker could not use this vulnerability to take complete control of a system," the advisory read.

"We have not been made aware of attacks that try to use the reported vulnerability or of customer impact at this time, but we are aggressively investigating the public reports," the advisory added.

Microsoft said that it will release a patch as soon as possible and is " aggressively investigating" reports of the flaw.

The vulnerability was discovered by security researcher Tom Ferris of SP (security-protocols) Research Labs. In a post on the Security-Protocols site, "badpack3t" wrote that they notified Microsoft about the flaw in May and allegedly were told that a patch would be out for it by August. SP Research Labs did not disclose the details of how to exploit the flaw nor did they provide proof of concept code along with their website posting.

While most Windows versions ship with RDP services disabled, Remote Desktop is turned on out-of-the-box in Windows XP Media Center Edition. Only computers using services that have RDP enabled are vulnerable, Microsoft said in its advisory.

Services with RDP include Terminal Services in Windows 2000 and Windows Server 2003, and Remote Desktop Sharing and Remote Assistance in Windows XP.

Until a patch is available, Microsoft suggests users block TCP port 3389 (the port used by RDP) on their firewall, disable Terminal Services or Remote Desktop if not required, or secure remote desktop connections using either Internet Protocol Security or a virtual private network connection.