for all you sysadmins...y'all might want to check this out...seems if you don't specifically "say" you don't want someone messin about in your system...it can be construed as an invitation ...and may make prosecution difficult...

from NSA's Guide to Securing Microsoft
Windows 2000 Group Policy:
Security Configuration Tool Set

Message text for users attempting to log on
It is recommended that systems display a warning
message before logon, indicating the private nature of the
system. Many organizations use this message box to
display a warning message that notifies potential users
that their use can be monitored and they can be held
legally liable if they attempt to use the computer without
proper authorization. The absence of such a notice could
be construed as an invitation, without restriction, to enter
and browse the system.
HKLM\Software\Microsoft\Windows\CurrentVersion\
Policies\System\LegalNoticeText = "Text you want
displayed"

Sample Text...
“This is a Department of Defense computer system. This computer system, including all
related equipment, networks, and network devices (specifically including Internet access),
is provided only for authorized U. S. Government use. DoD computer systems may be
monitored for all lawful purposes, including to ensure that their use is authorized, for
management of the system, to facilitate protection against unauthorized access, and to
verify security procedures, survivability, and operational security. Monitoring includes
active attacks by authorized DoD entities to test or verify the security of this system.
During monitoring, information may be examined, recorded, copied, and used for
authorized purposes. All information, including personal information, placed on or sent
over this system may be monitored. Use of this DoD computer system, authorized or
unauthorized, constitutes consent to monitoring of this system. Unauthorized use may
subject you to criminal prosecution. Evidence of unauthorized use collected during
monitoring may be used for administrative, criminal or adverse action. Use of this system
constitutes consent to monitoring for these purposes."


Windows 2000 displays a message box with a caption and text that can be configured
before a user logs on to the machine. The DoD requires organizations to use this
message box to display a warning that notifies users that they can be held legally liable if
they attempt to log on without authorization to use the computer. The absence of such a
notice could be construed as an invitation, without restriction, to log on to the machine
and browse the system.