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.