Windows NT/2000 hole can let attacker take over systems

A recently discovered security vulnerability in a software debugging component of Microsoft Corp.’s Windows NT and 2000 operating systems can allow an attacker to elevate their privileges on a system and take the system over, according to intrusion detection system vendor Entercept Security Technologies Inc. An exploit is already circulating among potential attackers, the company said.

Entercept is set to release details on the vulnerability later Thursday in an alert to its customers, security e-mail lists and the press. An initial posting about the issue was made to the Bugtraq security list on March 14th.

The vulnerability relates to the way Windows NT and 2000 handle debug processes, according to Robin Matlock, senior vice president of marketing and services at Entercept. Normally, when a user initiates a debug session, that session is handed off to a software gateway that determines whether the request has the proper permission to be passed on to another software component, the Session Manager, she said. If the request is passed on, it is then executed in privileged mode, she said.

The security flaw, however, allows any program to initiate a debugging session and bypass the gateway step, thereby operating in privileged mode even if the user does not have that access, she said. This could allow an attacker to read, modify and delete files, she said.

Though there is an exploit in existence in the attacker community, the security hole cannot be easily attacked over a network, Matlock said. The exploit has been online for about a week, she said.

Microsoft does not yet have a patch for the vulnerability, though it is working on one, according to a statement from the company. Microsoft was contacted on March 11 about the issue, according to the company. In its statement, Microsoft said that “responsible security researchers work with the vendor of a suspected vulnerability issue to ensure that countermeasures are developed before the issue is made public and customers are needlessly put at risk.”

Entercept chose to release information about the vulnerability in the absence of a patch because of the exploit, said Matlock.

“If the hacking community knows about it and the user community doesn’t, that doesn’t help anyone,” she said. Entercept has a responsibility to help educate users, she added.

The education process in this instance may be difficult, however, as standard intrusion detection systems will not detect exploitation of this vulnerability, according to Matlock. In the view of most host- and behavior-based intrusion detection systems the actions taken to exploit the hole will seem normal, thus bypassing their protection, she said.

Users can protect themselves by downloading workaround code from the Web site of a German computer security organization located at

Entercept’s security bulletin recommends the use of its products as the best way to prevent exploitation of the vulnerability.

In a written statement, Microsoft said it is currently investigating the issue.

“It’s worth noting that third parties can choose to post possible workaround procedures for an alleged issue without completing the intensive investigation undertaken by the vendor,” the statement read.

“We are concerned that this report has gone public before we’ve had a fair chance to investigate it – Its publication may cause our customers needless confusion and apprehension or possibly even put them at risk,” Microsoft said.