F-SHELL - Scanner and disinfector for the Shell.10634 virus Copyright (c) 1996 Data Fellows Ltd OVERVIEW F-SHELL will detect and disinfect the Shell.10634 Windows virus (also known as Tentacle_II). This document gives a brief description of the Shell virus and explains how to use F-SHELL to detect and disinfect this virus. ABOUT THE Shell VIRUS Shell is one of an increasing number of viruses distributed via the Internet, in the form of posts to Usenet News. This virus was found in the wild in June 1996 in USA, UK, Australia, Norway and New Zealand. It has possibly been distributed over the internet several times. A known infection happened on the 3rd of August, 1996, when an infected screen saver called PCTRSHOW.ZIP was posted to the following newsgroups: alt.sex.pictures alt.binaries.pictures.erotica alt.binaries.pictures.erotica.blondes alt.binaries.pictures.erotica.breasts alt.binaries.pictures.erotica.cheerleaders alt.binaries.pictures.erotica.female alt.binaries.pictures.erotica.lesbians alt.binaries.pictures.erotica.oral alt.binaries.pictures.erotica.orientals alt.binaries.pictures.erotica.redheads alt.binaries.pictures.erotica.teen alt.binaries.pictures.erotica.teen.female alt.binaries.pictures.erotica.voyeurism alt.binaries.pictures.erotica.young alt.binaries.pictures.groupsex alt.binaries.pictures.erotica.latina alt.binaries.pictures.celebrities alt.binaries.pictures.girls The virus infects only Windows 3.x executables (NE), and it does it without changing the executable entry point. This is an unusual infection method and was first introduced in this virus. The virus adds a new segment to the executable and modifies the structure of the file: this makes it a very difficult virus to disinfect. When executed, Shell searches the directory tree for suitable files to infect. Only EXE and SCR (screen saver) files can get infected. Also 32bit Win95 and WinNT executables can be infected by the virus, but these files are unable to spread the infection further. Shell does not stay resident in memory. This virus activates by dropping a GIF file, which contains a picture of a Shell and text: I'm the Tentacle Virus! SYMPTOMS Shell causes no obvious symptoms, except slowing the PC down (the infection process is slow). For this reason it is recommended that suspect PCs be scanned using the F-SHELL utility. HOW TO USE F-SHELL Run F-SHELL with the drive letter of directory as a parameter. For example: F-SHELL C: F-SHELL Z:\USERS If F-SHELL finds the virus, you will be notified. Then, type F-SHELL /DISINF, and F-SHELL will disinfect any infected files. IMPORTANT: It is not always possible to recover an infected file completely. The file will usually work after disinfection, but is not an exact copy of the original. We recommend reinstalling and restoring infected files instead of disinfecting them. Disinfected files will almost always work correctly, unless the program has a self-check routine. MS Mail and MS Schedule are examples of programs which will warn about failed self-check after disinfection. WHAT ABOUT FLOPPIES? Since infected files may have been copied to floppy diskettes, you will want to scan your floppy diskettes as well. To do this, invoke F-SHELL using the /MULTI switch (eg F-SHELL A: /MULTI). -- Virus analysis based on information from Mikko Hypponen, Data Fellows F-PROT Professional Support. F-SHELL by Peter Szor, Data Fellows F-PROT Professional Development. F-SHELL is protected by international copyright laws. F-SHELL is (c) 1996 Data Fellows Ltd, and it is not in public domain or freeware, but you are free to use and share this software with no charges in non-commercial private use. Use of this software in other environments is not allowed in Europe, Asia and Africa without a license to F-PROT Professional or a current license from Frisk Software International. To purchase a license, contact your local distributor listed in PRO.DOC. Please redistribute F-SHELL only with this documentation. You are not allowed to resell this software for your own profit (normal copying costs excluded) or claim to hold rights to this software. Although you may have the right to use F-SHELL, it will remain the exclusive property of Data Fellows. Data Fellows does not warrant that the software is error free and we will not cover any costs created by function or malfunction of this program. Data Fellows also disclaims liability for possible consequential damages. If you cannot agree to these restrictions, you should not use F-SHELL. Copyright (c) 1996 Data Fellows Ltd, Finland Data Fellows Ltd Paivantaite 8 FIN-02210 ESPOO FINLAND tel: +358-9-478 444 fax: +358-9-478 44 599 e-mail: F-PROT-Support@DataFellows.com www: http://www.DataFellows.com/