Flaw in Win2000, NT4.0 makes domains 'too trusting'

A flaw in the way Microsoft's Windows 2000 and NT 4.0 server operating systems authenticate users across domains could allow somebody with administrator privileges to extend that power to other domains, Microsoft warned Wednesday.

Although the flaw is "extremely difficult" to exploit, the worst case scenario associated with it is "serious," Microsoft said in a security bulletin. Administrators are encouraged to consider installing a software fix, if physical and personnel security considerations indicate sufficient risk, the software maker said.

The flaw lies in the trust relationships between network domains in Windows 2000 and NT 4.0 environments. The trusting domain does not verify that the trusted domain is actually authoritative for all the SIDs (security identifiers) in the authorization data, allowing an attacker to increase his or her access level, Microsoft said.

Trust relationships are commonly used in Windows 2000 and NT 4.0 environments. They are created between network domains to allow users in one domain to access resources in another domain without having to authenticate themselves. When a user in a trusted domain requests access to a resource in a trusting domain, the trusted domain supplies authorization data in the form of a list of SIDs, that indicate a user's identity and group membership.

To exploit the flaw, an attacker has to add SIDs to the authorization data of the trusted domain. To do this, the attacker needs administrator privileges on the trusted domain, as well as the technical knowledge to modify low-level operating system functions and data structures, as Windows NT 4.0 and 2000 don't offer a tool to add desired SIDs, Microsoft said.

The trusting domain is "too trusting" when judging the SIDs in the authorization data, Microsoft said. The attacker, an administrator in the trusted domain with, for example, mere read-only rights in the trusting domain, could add an SID that identifies him or her as an administrator of the trusting domain. This would give full access over the computers in that domain.

The vulnerability can be eliminated with a new SID Filtering tool, Microsoft said. The fix sets the system up to inspect authorization data and remove SIDs that don't belong to the originating domain.

Installing SID Filtering could have side effects, Microsoft cautioned. Legitimate SIDs that do not come from the originating domain are also filtered. This could, for example, result in trouble for users that are migrating from NT 4.0 to 2000 and using a feature called SIDHistory. SIDHistory is used to ease migration before new access control lists can be created for resources, Microsoft said.

Microsoft provides more information on SID Filtering in a white paper on its TechNet Web site: http://www.microsoft.com/windows2000/techinfo/administration/security/sidfilter.asp

Join the newsletter!

Or

Sign up to gain exclusive access to email subscriptions, event invitations, competitions, giveaways, and much more.

Membership is free, and your security and privacy remain protected. View our privacy policy before signing up.

Error: Please check your email address.
Keep up with the latest tech news, reviews and previews by subscribing to the Good Gear Guide newsletter.

Joris Evers

Computerworld
Show Comments

Brand Post

Most Popular Reviews

Latest Articles

Resources

PCW Evaluation Team

Andrew Teoh

Brother MFC-L9570CDW Multifunction Printer

Touch screen visibility and operation was great and easy to navigate. Each menu and sub-menu was in an understandable order and category

Louise Coady

Brother MFC-L9570CDW Multifunction Printer

The printer was convenient, produced clear and vibrant images and was very easy to use

Edwina Hargreaves

WD My Cloud Home

I would recommend this device for families and small businesses who want one safe place to store all their important digital content and a way to easily share it with friends, family, business partners, or customers.

Walid Mikhael

Brother QL-820NWB Professional Label Printer

It’s easy to set up, it’s compact and quiet when printing and to top if off, the print quality is excellent. This is hands down the best printer I’ve used for printing labels.

Ben Ramsden

Sharp PN-40TC1 Huddle Board

Brainstorming, innovation, problem solving, and negotiation have all become much more productive and valuable if people can easily collaborate in real time with minimal friction.

Sarah Ieroianni

Brother QL-820NWB Professional Label Printer

The print quality also does not disappoint, it’s clear, bold, doesn’t smudge and the text is perfectly sized.

Featured Content

Product Launch Showcase

Latest Jobs

Don’t have an account? Sign up here

Don't have an account? Sign up now

Forgot password?