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 & 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.
Microsoft Windows 2000
This vulnerability requires an administrative procedure rather than a patch. The needed changes are discussed in the FAQ.