ZAPPER ====== by Paul Thomsen Introduction: ------------- In the continuiing effort to improve system performance and security, the new 'ZAPPER' program is a useful and effective tool. This function will automatically log any and all users off the system if they have been logged in without doing any work for a certain period of time. Thus unattended terminals cannot be used to effect the system in any way, and the system's overhead is reduced so that it can do more work to serve the active users. The allowable time period that users can be logged in without doing any terminal work varies for each application and potentially for each user. Thus different users are logged out at different times. All open files are closed for the user when he is logged out. Operation: ---------- The ZAPPER program looks for all interactive sessions, and deletes those that have been inactive for too long. In order to determine how long is too long, it reads two sequential files containing such information for the users, or it uses a default pre-programmed time ( 30 minutes ). The first file is SYS$SYSTEM:ZAPPER_APPLICATIONS.DAT, which contains image names and how long users using these images are allowed to be inactive. For instance, all ADT users ( training, production, etc. ) run ADTMAIN, and this might have an inactive time limit of 45 minutes. The second file will override this file for specific users that might be exceptional. This file is called SYS$SYSTEM:ZAPPER_USERS.DAT. These files are read by ZAPPER only when it is first started up, so if changes are to be made, the files should be edited and the programn then re-submitted, as follows. For convenience, the ZAPPER data files are ASCII sequential files and can be edited with EDT, etc. The instructions for their use are within the files themselves. In normal operation, ZAPPER maintains a list of users who were on the system one minute ago. After 'hibernating' for 1 minute, ZAPPER will wake up and compare the list to the current situation on the system, updating the list as it goes. For each user currently on the system, it will note whether they have had any activity in the last minute. If not, it will increase its record of how long they have been inactive. At the same time it will check these users to see if they have now exceeded their allowable inactive periods. Those that have will have messages displayed on their screen, as follows. The time and date that the user was logged out is also recorded in a log file ( SYS$SYSTEM:ZAPPER.LOG). Any time a user is noted to have had activity, his recorded inactive time is automatically zeroed. If a user is no longer on the system, he will be deleted from the list of past users. For normal calculations of inactive periods, the use of cpu time by the process between the two test points is used as the indicater of acitivity. However, between the warning and final message to the user the buffered and direct I/O's are also checked. Thus hitting will be sufficient to keep the process active after the warning message. Justing hitting random characters may not be, since these may be intercepted by the terminal server and not have any effect on the processor. User messages: -------------- The following message will appear when the user is due to be logged out: ATTENTION - You will be Z A P P E D for inactivity in 1 minute. Hit to avoid being Z A P P E D. Two beeps will also sound at this time to catch his attention. At this point he can hit the Return or Enter keys, or any Gold or control ( Ctrl ? ) function keys. If he does not hit one of these keys within one minute of this message appearing, he will be logged off the system in an orderly manner and the following message will be displayed: ATTENTION - You have been Z A P P E D for inactivity. When the user returns to his terminal he may log back in as he usually does. Test Modes: ----------- In order to fully ( hopefully ) verify the logic and operation of ZAPPER at any time, the ZAPPER program has two variables which, when appropriately set, will dump out all significant variables from the program. Most will be recorded in the log file, but some may also appear on the screen of the person to be zapped. The first technique is affected by giving 'test' the value of "YES". The second is affected by assigning to 'tester' the username of the person wishing to test ZAPPER. The tester can then verify that all and only people deserving to be logged out are, and that the end-user warning messages are working as intended. The first technique also dumps the values read from the data files, so that they can be verified as working properly. Naturally, when the program is not being tested these variables should be set to null, in order to minimize the size of the log file and speed operation slightly. Submission: ----------- To submit the ZAPPER for running the system manager should @SYS$SYSTEM:ZAPPER. This will create a detached process with the appropriate privileges and output mechanisms. If ZAPPER is already running on the node it will delete the older process first before creating the new one. This will allow any changes to allowable inactive times to take effect and release the previous version of the log file to be released for inspection. ZAPPER only deletes processes from the processor that it is working on, so it should be started on each node that the system manager wishes it to work on. It may be undesirable to log off some users at any time. Therefore the time out value for those users or their images should be st set at 999999. As a double check against this problem the program is currently setup to also not boot off users with UIC's ending in 00. This is a value that is appropriate to my site, but you may wish to change this value at your site, or comment out that logic altogether. ( You may note that in the program this variable actually refers to 64, but this is decimal, which is more natural to BASIC, while 100, etc., is in octal, which is more natural to VMS ). ****** And here's something you might like to use as an introduction you can give to your users... New Zapper Program ------------------ In our continuiing efforts to improve system performance and security, Technical Support will be introducing a new automatic function to the system. This should begin during the morning of ( whatever date ). This function, which we call 'Zapper', will automatically log any and all users off the system if they have been logged in without doing any work for a certain period of time. Thus unattended terminals cannot be used to effect the system in any way, and the system's overhead is reduced so that it can do more work to serve the users. The allowable time period that users can be logged in without doing any terminal work varies for each application and potentially for each user. Thus different users are logged out at different times, as per the table at the end of this note. The following message will appear when the user is due to be logged out: ATTENTION - You will be Z A P P E D for inactivity in 1 minute. Hit to avoid being Z A P P E D. Two beeps will also sound at this time to catch your attention. At this point you can hit the Return or Enter keys, or any Gold or control ( Ctrl ? ) function keys. If you do not hit one of these keys within one minute of this message appearing, you will be logged off the system in an orderly manner and the following message will be displayed: ATTENTION - You have been Z A P P E D for inactivity. When you return to your terminal you may log back in as you usually do.