Keystroke Logging Banner
Original issue date: December 7, 1992
Last revised: September 19, 1997
Attached copyright statement
A complete revision history is at the end of this file.
The CERT Coordination Center has received information from the United States
Department of Justice, General Litigation and Legal Advice Section, Criminal
Division, regarding keystroke monitoring by computer systems administrators,
as a method of protecting computer systems from unauthorized access.
The information that follows is based on the Justice Department's advice
to all federal agencies. CERT strongly suggests adding a notice banner
such as the one included below to all systems. Sites not covered by U.S.
law should consult their legal counsel.
The legality of such monitoring is governed by 18 U.S.C. section 2510
et seq. That statute was last amended in 1986, years before the words
"virus" and "worm" became part of our everyday vocabulary. Therefore,
not surprisingly, the statute does not directly address the propriety
of keystroke monitoring by system administrators.
Attorneys for the Department have engaged in a review of the statute
and its legislative history. We believe that such keystroke monitoring
of intruders may be defensible under the statute. However, the statute
does not expressly authorize such monitoring. Moreover, no court has
yet had an opportunity to rule on this issue. If the courts were to
decide that such monitoring is improper, it would potentially give rise
to both criminal and civil liability for system administrators.
Therefore, absent clear guidance from the courts, we believe it is
advisable for system administrators who will be engaged in such
monitoring to give notice to those who would be subject to monitoring
that, by using the system, they are expressly consenting to such
monitoring. Since it is important that unauthorized intruders be given
notice, some form of banner notice at the time of signing on to the
system is required. Simply providing written notice in advance to only
authorized users will not be sufficient to place outside hackers on
An agency's banner should give clear and unequivocal notice to
intruders that by signing onto the system they are expressly consenting
to such monitoring. The banner should also indicate to authorized
users that they may be monitored during the effort to monitor the
intruder (e.g., if a hacker is downloading a user's file, keystroke
monitoring will intercept both the hacker's download command and the
authorized user's file). We also understand that system administrators
may in some cases monitor authorized users in the course of routine
system maintenance. If this is the case, the banner should indicate
this fact. An example of an appropriate banner might be as follows:
This system is for the use of authorized users only.
Individuals using this computer system without authority, or in
excess of their authority, are subject to having all of their
activities on this system monitored and recorded by system
Each site using this suggested banner should tailor it to their precise
needs. Any questions should be directed to your organization's legal
In the course of monitoring individuals improperly using this system,
or in the course of system maintenance, the activities of authorized
users may also be monitored.
Anyone using this system expressly consents to such monitoring and is
advised that if such monitoring reveals possible evidence of criminal
activity, system personnel may provide the evidence of such monitoring
to law enforcement officials.
The CERT Coordination Center wishes to thank Robert S. Mueller, III,
Scott Charney and Marty Stansell-Gamm from the United States Department
of Justice for their help in preparing this Advisory.
This document is available from:
CERT/CC Contact Information
Phone: +1 412-268-7090 (24-hour hotline)
Fax: +1 412-268-6989
CERT Coordination Center
Software Engineering Institute
Carnegie Mellon University
Pittsburgh PA 15213-3890
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Monday through Friday; they are on call for emergencies during other
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Copyright 1992 Carnegie Mellon University.
September 19,1997 Attached copyright statement