[W2K]MS02-064: Windows 2000 Default Permissions


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Title: Windows 2000 Default Permissions Could Allow Trojan Horse

Program (Q327522)

Date: 30 October 2002

Software: Windows 2000

Impact: Trojan Horse program execution

Max Risk: Moderate

Bulletin: MS02-064

Microsoft encourages customers to review the Security Bulletin at:

http://www.microsoft.com/technet/security/...in/MS02-064.asp.

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Issue:

======

On Windows 2000, the default permissions provide the Everyone group

with Full access (Everyone:F) on the system root folder

(typically, C:\). In most cases, the system root is not in the search

path. However, under certain conditions - for instance, during logon

or when applications are invoked directly from the Windows desktop

via Start | Run - it can be.

This situation gives rise to a scenario that could enable an attacker

to mount a Trojan horse attack against other users of the same

system, by creating a program in the system root with the same name

as some commonly used program, then waiting for another user to

subsequently log onto the system and invoke the program. The Trojan

horse program would execute with the user's own privileges, thereby

enabling it to take any action that the user could take.

The simplest attack scenario would be one in which the attacker knew

that a particular system program was invoked by a logon script. In

that case, the attacker could create a Trojan horse with the same

name as the system program, which would then be executed by the

logon script the next time someone logged onto the system. Other

scenarios almost certainly would require significantly greater user

interaction - for instance, convincing a user to start a particular

program via Start | Run - and would necessitate the use of social

engineering.

The systems primarily at risk from this vulnerability would be

workstations that are shared between multiple users, and local

terminal server sessions. Other systems would be at significantly

less risk:

- Workstations that are not shared between users would be at no

risk, because the attacker would require the ability to log onto

the system in order to place the Trojan horse.

- Servers would be at no risk, if standard best practices have

been followed that advocate only allowing trusted users to log

onto them.

- Remote Terminal server sessions would be at little risk,

because each user's environment is isolated. That is, the system

root is never the current folder - instead, the user's Documents

and Settings folder is, but the permissions on this folder would

not enable an attacker to place a Trojan horse there.

Mitigating Factors:

====================

- An attacker would require the ability to log onto the system

interactively in order to place the Trojan horse program. It

could not be placed remotely

- As discussed above, dedicated workstations, servers and remote

terminal server sessions would be at less risk (or, in some cases,

none at all) from the vulnerability.

Risk Rating:

============

- Internet systems: Low

- Intranet systems: Low

- Client systems: Moderate

Patch Availability:

===================

- This vulnerability requires an administrative procedure rather

than a patch. The needed changes are discussed in the FAQ.

Please read the Security Bulletin at

http://www.microsoft.com/technet/security/...in/ms02-064.asp

for information on obtaining this patch.

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