________________________________________________________________________ THE COMPUTER INCIDENT ADVISORY CAPABILITY CIAC INFORMATION BULLETIN ________________________________________________________________________ Logon Messages and Hacker/Cracker Attacks March 16, 1990, 1200 PST Number A-22 CIAC has published several recent information bulletins and advisory notices about hacker/cracker attacks on computers connected to the Internet. This bulletin suggests a strategy for your site that is important for legal reasons. In addition, this strategy may help deter some hacking activity. In many systems a logon screen is displayed during or before the time the user is asked to enter a user name and password. Sometimes this screen contains a message which welcomes the potential user to the system. Court cases involving unauthorized use of computing systems may be thrown out because a welcoming message was initially displayed. We strongly recommend, therefore, that (when feasible to implement) every machine at your site should display a warning message before or during the logon sequence, and that all phrases suggesting that users are welcome to use the system be removed. An example of a warning message is the following: WARNING: Unauthorized access to this computer system is prohibited, and is subject to criminal and civil penalties. This type of warning message may also discourage casual hackers from intruding into a system. If feasible to implement, it is also important to display to users any failed logon attempts on their account, and to inform users who they should contact if their account was probed or accessed by someone else. Finally, we recommend that the logon screen should advise users to logout when they are through with a session or when they leave their terminal. For additional information or assistance, please contact CIAC: Eugene Schultz (415) 422-8193 or (FTS) 532-8193 FAX: (415) 423-0913 or (415) 422-4294 You may also send e-mail to: ciac@tiger.llnl.gov Neither the United States Government nor the University of California nor any of their employees, makes any warranty, expressed or implied, or assumes any legal liability or responsibility for the accuracy, completeness, or usefulness of any information, product, or process disclosed, or represents that its use would not infringe privately owned rights. Reference herein to any specific commercial products, process, or service by trade name, trademark manufacturer, or otherwise, does not necessarily constitute or imply its endorsement, recommendation, or favoring by the United States Government or the University of California. The views and opinions of authors expressed herein do not necessarily state or reflect those of the United States Government nor the University of California, and shall not be used for advertising or product endorsement purposes.