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Home : Advisories : Keystroke Logging Banner

Title: Keystroke Logging Banner
Released by: CERT
Date: 7th December 1992
Printable version: Click here

Hash: SHA1


Last Revised:  September 19,1997

                Attached copyright statement


                                 CERT Advisory

                                December 7, 1992

                            Keystroke Logging Banner

- -----------------------------------------------------------------------------

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


       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.

- -----------------------------------------------------------------------------

Each site using this suggested banner should tailor it to their precise

needs.  Any questions should be directed to your organization's legal


- -----------------------------------------------------------------------------

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.

- -----------------------------------------------------------------------------

If you believe that your system has been compromised, contact the CERT

Coordination Center or your representative in FIRST (Forum of Incident

Response and Security Teams).

Internet E-mail: cert@cert.org

Telephone: 412-268-7090 (24-hour hotline)

           CERT personnel answer 7:30 a.m.-6:00 p.m. EST(GMT-5)/EDT(GMT-4),

           on call for emergencies during other hours.

CERT Coordination Center

Software Engineering Institute

Carnegie Mellon University

Pittsburgh, PA 15213-3890

Past advisories, information about FIRST representatives, and other

information related to computer security are available for anonymous FTP

from cert.org (

- ------------------------------------------------------------------------------

Copyright 1992 Carnegie Mellon University. Conditions for use, disclaimers,

and sponsorship information can be found in

http://www.cert.org/legal_stuff.html and http://ftp.cert.org/pub/legal_stuff .

If you do not have FTP or web access, send mail to cert@cert.org with

"copyright" in the subject line.

CERT is registered in the U.S. Patent and Trademark Office.


Revision History:

September 19,1997  Attached Copyright Statement


Version: PGP for Personal Privacy 5.0

Charset: noconv





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