_______________________________________________________________________________ Nomad Mobile Research Centre A D V I S O R Y www.nmrc.org Simple Nomad [thegnome@nmrc.org] 05May1999 _______________________________________________________________________________ Platform : Microsoft NT 4.0 Application : Network Associates' VirusScan NT Severity : Medium Synopsis -------- Network Associates VirusScan NT (formerly McAfee VirusScan NT) version 4.0.2 does not properly update virus signature definition files under certain conditions, and will falsely report it is up to date during manual updates. This impacts both NT Server and Workstation. Tested configuration -------------------- Microsoft NT Server 4.0 w/SP3, Network Associates VirusScan NT version 4.0.2. Microsoft NT Workstation 4.0 w/SP3 and SP4, Network Associates VirusScan NT version 4.0.2. Pre-4.0.2 versions of VirusScan NT were not tested, nor were versions for other platforms, such as Windows 95 or 98. Bug(s) report ------------- Network Associates VirusScan NT has a feature that allows for a user to update the virus definitions file via ftp. This task can also be automated via the VirusScan NT AntiVirus Console. In version 4.0.2, the scan engine holds open the main definition file scan.dat (located in the VirusScan NT directory) during the ftp process, preventing the file from being overwritten with the new version. The engine itself apparently does not check return codes and will not notify the user that the file was not updated. Worse, the Application Log is updated as if the install completed properly, therefore subsequent downloads of new definition files will not update the scan.dat properly. Subsequent manual downloads will in fact tell you that you already have the latest definition file when in fact you do not. NMRC was not able to make this error occur consistently, and we strongly suspect that a race condition exists where the updates will occasionally work, but we were able to duplicate the error condition most of the time. Testing was done in NMRC labs, and at two corporate locations. To verify the proper definitions file, check the About box from the AntiVirus Console program for the latest date next to the text "Created On". If after a manual or automatic update this date does not change, your definitions have not been properly updated. The implication here is that the administrator or end user believes their system is protected when it in fact is not. Solution/Workaround ------------------- Upgrade to Network Associates VirusScan NT version 4.0.3a, which resolves the problem. Alternately, disable the VirusScan engine, wait several seconds for the operating system to close the file, and manually copy the definition files into the VirusScan NT directory. This second method will place your log files out of sync with the definition files until the next manual or automatic download, but this should not impact functionality. It is recommended that you disable 4.0.2 (or even uninstall) before performing an upgrade to 4.0.3a due to other problems we encountered during the testing of this product, such as being unable to properly stop the VirusScan services before upgrading. Once again, these problems were inconsistent but happened several times on several systems. One further note, in a restricted NT workstation environment, it is next to impossible to have the user upgrade the product themselves. Local admin rights are required to make this happen, and this will require a visit from an individual with adequate rights to the workstation to complete the upgrade. Comments -------- Network Associates has been notified and recommend the upgrade to 4.0.3a to resolve the problem. This problem was discovered while investigating why upgraded machines were still infected by various Microsoft Word macro virii after they had been upgraded to the latest definition files. Network Associates can be reached at http://www.nai.com/. Unfortunately at the time of this writing the ftp location of the 4.x definition files was not present. It's supposed to be at ftp://ftp.nai.com/pub/antivirus/update/4.x but had disappeared from the server(s). _______________________________________________________________________________