Virus Bulletin, November 1990

November 1990 ISSN 0956-9979 THE AUTHORITATIVE INTERNATIONAL PUBLICATION ON COMPUTER VIRUS PREVENTION, RECOGNITION AND REMOVAL Editor: Edward Wilding Technical Editor: Fridrik Skulason, University of Iceland Editorial Advisors: Jim Bates, Bates Associates, UK, Phil Crewe, Fingerprint, UK, Dr. Jon David, USA, David Ferbrache, Information Systems Integrity & Security Ltd., UK, Ray Glath, RG Software Inc., USA, Hans Gliss, Datenschutz Berater, West Germany, Ross M. Greenberg, Software Concepts Design, USA, Dr. Harold Joseph Highland, Compulit Microcomputer Security Evaluation Laboratory, USA, Dr. Jan Hruska, Sophos, UK, Dr. Keith Jackson, Walsham Contracts, UK, Owen Keane, Barrister, UK, Yisrael Radai, Hebrew University, Israel, John Laws, RSRE, UK, David T. Lindsay, Digital Equipment Corporation, UK, Martin Samociuk, Network Security Management, UK, John Sherwood, Sherwood Associates, UK, Dr. Ken Wong, BIS Applied Systems, UK, Ken van Wyk, CERT, USA. CONTENTS FOR PROGRAMMERS Virus Encryption Techniques 13 EDITORIAL 2 VIRUS ANALYSIS TECHNICAL NOTES 3 WHALE MAC THREATS - A Dinosaur Heading for Extinction 17 MDEF C 4 ADDENDUM FROM THE FIELD Jonah’s Journey 4K - A Warning of Data - A Complementary Report 20 Corruption 5 FOR MANAGEMENT PRODUCT REVIEW PC Security Part I. Controlling the HyperACCESS/5 - A Virus Operating System 7 Filtering COMMS Package 21 END-NOTES & NEWS 24 KNOWN IBM PC VIRUSES 11 VIRUS BULLETIN ©1990 Virus Bulletin Ltd, 21 The Quadrant, Abingdon Science Park, Oxon, OX14 3YS, England. Tel (+44) 235 555139. /90/$0.00+2.50 This bulletin is available only to qualified subscribers. No part of this publication may be reproduced, stored in a retrieval system, or transmitted by any form or by any means, electronic, magnetic, optical or photocopying, without the prior written permission of the publishers. Page 2 VIRUS BULLETIN November 1990 constantly updated, is available in the event that the police EDITORIAL should require technical support pending an arrest or prosecu- tion. Hope Springs Eternal Slowly but surely, an informal network is developing which can respond to the threat of malicious software. However, to be Some beneficial developments have arisen in the wake of the truly effective it will need to be formalised and properly WHALE virus (which is reported in two separate articles in funded. Regrettably, this is appears unlikely to happen until a this month’s edition, see pp. 17-20). genuine disaster occurs. Initial analysis suggested that this particular program would be Cutting Out the Middle-Men a ‘tough nut to crack’ and it soon became clear that collabora- tion between researchers would be necessary to accelerate the There is a well-founded suspicion that certain virus writers, process of disassembly. far from wishing to cause computer havoc, are simply seeking publicity and/or notoriety for their programs. In fact, ad hoc arrangements to minimise the duplication of analysis and harmonise the disassembly process emerged The fastest, easiest way to do this is to send a virus directly to within days of the program’s discovery. Information and a researcher, usually anonymously or, as happened on at least annotated disassemblies were transferred (in encrypted form) one occasion, by claiming that the sample was ‘found’. by e-mail among a central corps of programmers. The priority Documented incidents include the appearance of the TP series, was to find a method by which the virus could be detected Murphy-2, New Vienna, SVIR and Icelandic-2. consistently - WHALE obligingly “lifted her skirts” and a number of proven detection methods have now been identified. There have been some instances whereby a sample made (These methods are not being published but are available to available for disassembly was atypical - it contained additional bona fide anti-virus software developers through VB.) text strings or replication code was absent. In some of these cases this would only be possible if the virus had been sent The most encouraging aspect of this process was the unparal- directly by its writer or a close associate. leled cooperation and consultation between the various researchers and programmers involved.The strengthening of The original Datacrime virus is understood to have been sent communications links and increased cooperation among directly to a researcher, which may explain its apparent non- researchers should significantly reduce the response time in existence in the wild. (Not one incident of any of the Datac- analysing rogue software in the event of a future emergency. rime family actually triggering has been reported to VB this year, a statistic confirmed by other organisations active in the Various initiatives are currently under way in the United field.) Kingdom to establish a government- and/or industry-funded research and reporting centre along similar lines to the This phenomenon, whereby the virus is sent directly to a Computer Emergency Response Team in the United States or research specialist is referred to as “cutting out the middle- the Information Security Research Centre at the Queensland man”. The situation makes virus researchers analogous to University of Technology, Australia. It is important that any lightning conductors and might be construed as beneficial - equivalent British centre is devoid of commercial interests or dangerous code ends up in the hands of those best qualified to affiliation. This would suggest that it should be controlled by deal with it. an academic or government body. VB hopes to be able to report some ‘concrete’ initiatives presently. Unfortunately, each such sample has to undergo the same painstaking analysis as other malicious software because there There is also an air of cautious optimism that MS-DOS and is no guarantee that the virus can be isolated - the originator PC-DOS virus code is reaching its defined limits. Thorough could still release the virus into the wild, if he has not already study of undocumented operating system features has proved done so. very helpful in analysing some of the latest computer viruses while standard virus writing tricks are becoming ever more Suggestions have been made that the VB Table of Known IBM readily identifiable. The ‘armoured’ viruses, of which WHALE PC Viruses should reflect whether or not entries are likely to is the most tortuous, convoluted and ludicrous, are a sign of be encountered in the real world as opposed to being isolated resignation by the virus writers; the defensive bulk which they or laboratory specimens. It would certainly be feasible to carry actually increases the likelihood of detection. indicate the set of forty or so viruses and variants which are currently known to be causing genuine infections. However, to An additional benefit of ongoing research is the mass of dismiss functioning viruses of dubious origin as being of no forensic evidence which accumulates and which is carefully consequence would be folly - the research community is simply indexed for future reference. This information, which is not in a position to categorise them as such. VIRUS BULLETIN ©1990 Virus Bulletin Ltd, 21 The Quadrant, Abingdon Science Park, Oxon, OX14 3YS, England. Tel (+44) 235 555139. /90/$0.00+2.50 This bulletin is available only to qualified subscribers. No part of this publication may be reproduced, stored in a retrieval system, or transmitted by any form or by any means, electronic, magnetic, optical or photocopying, without the prior written permission of the publishers. November 1990 VIRUS BULLETIN Page 3 the Anthrax virus, which may indicate that both viruses were TECHNICAL NOTES written by the same author, probably the person calling himself ‘Dark Avenger’. When the Anthrax virus infects a disk, it will place a copy of High Level Languages itself on the last track of the disk in addition to infecting the Although most viruses are clearly written in assembly lan- boot sector. If the original boot sector is restored by some anti- guage, it is possible to use a high-level language such as C or virus program or utility which does not overwrite the last track, Pascal instead. Several such viruses are known today, includ- the disk will contain an inactive but functional copy of the ing AIDS, AIDS-2 and Kamikaze, but their number is low virus, even after it has seemingly been disinfected. The 2100 compared to the 250 or so different virus variants written in virus (itself a parasitic virus which infects COM and EXE assembly language. As writing in C or Pascal is undoubtedly files) is able to locate this “spare” copy of the Anthrax virus easier than writing in assembly language, some explanation and will reactivate its dormant code thus causing the boot must be sought. The High-Level Language viruses (HLL) sector to become reinfected. generally show evidence of being created by programmers with less knowledge than many of the assembly language viruses. Unintentional Side-Effects The reason may be that the assembly language programmers want their “creations” to reflect their ability -being able to It is well known that several viruses contain malicious code write a program in assembly language indicates a higher level intended to cause damage when some specific trigger condition of technical ability than being able to program in Pascal. is met. This damage usually involves formatting the hard disk, Another reason is that writing an advanced virus in “pure” C deleting programs or corrupting data. What is less well known or Pascal is difficult, as many interrupt level calls are required is the fact that some viruses may cause unintentional damage, for any function beyond simple replication. sometimes only when certain hardware is present. A characteristic of HLL viruses is their size - due to compiler A well documented example of unintentional damage is that overhead, a HLL virus may be ten times larger than an done by the New Zealand virus which can corrupt the FAT on equivalent assembly language virus. To the virus writer the some hard disks and which overwrites the third sector of the HLL virus offers one considerable advantage, which partially root directory corrupting 1.2 Mbyte 5.25" diskettes with more offsets this obvious drawback: it is difficult to select a usable than 32 files.

Load more