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Why Viruses Are and Always will be a Problem

Richard Ford
NCSA News, pages 5–7
April 1996

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Many people seem to believe that the virus threat can be held at bay by simply buying the latest and greatest scanner, holding on tight to one's security policy, and cleaning up when the inevitable happens. To all intents and purposes, the virus problem is solved, and the new challenge of the Internet beckons to MIS staff worldwide. Right? Wrong.

Nineteen-ninety-five has been an extremely busy year in terms of changes to commonly held beliefs about viruses. Policies need to be rewritten, detection techniques updated. Let us take a quick tour of 1995, and then turn our attention to the future, and see where these developments might lead....

Viruses and Data Files

The biggest "surprise" of 1995 was the discovery of the Word Macro virus Concept in the wild. The use of quotes around surprise is quite intentional, as virus researchers awaited such a development for many years: Dr. Harold Highland pointed out this possibility in 1989 [1]. The advent of this virus forces users to reexamine their beliefs about viruses, and forces administrators to make some quick changes to their anti-virus scanning methods; managers have had to adjust policy to reflect the reality now in our midst: Macro viruses.

The concept behind Macro viruses is very simple. Many application programs allow for the inclusion of certain macros within data files. As application software has developed, such macro languages have become increasingly powerful, allowing programmers to edit, delete and copy files, and even on occasion to invoke the DOS shell. For instance, one application package allows for at least 150 macro commands in each template. These commands can allow the programs to `do things' without user action. They can do these things automatically, via the embedded macros.

Although there are several different packages that are susceptible to Macro viruses, currently the most effected one is MicroSoft Word. There are also Macro viruses for Excel and AmiPro.

In order to better understand how these viruses function, let us examine the first widely-reported Macro virus, WinWord Concept, in detail.

When the user selects an MS-WORD document and loads it, either from within Word, or by double-clicking just on the document icon itself, Word examines the document type. A standard Word document cannot contain any macros embedded within it, and is simply loaded into the program, ready for editing. However, if the loaded file is a document template file, Word automatically loads any macros contained within it. Should the document template file contain a macro named `AutoOpen, ' the contents of this macro will be automatically executed. Concept utilizes this ability of the software by adding macros to existing documents. These macros, once installed, can add additional functionality to menu-bar operating, and allow the virus to infect other documents on the system. AutoOpen is not the only such autoexecuting macro in the Word environment. There are several others of which the programmer could have taken advantage. Although the Concept virus does not contain a trigger routine [2], the words "That's enough to prove my point" are contained within it.

Concept is rapidly becoming a very widespread virus. The reason for this is twofold. First, while users rarely share executables or boot from diskette, a large part of their job involves the exchange of data files. Furthermore, many (most?) company policy and procedure manuals do not address the risk posed by Macro viruses whatsoever. Since there are now actual implementations of this threat type, policy and procedure manuals need to be updated. In many cases, the anti-virus product vendor can supply the necessary information. Second, the most widespread Macro virus, Concept, was accidentally distributed via CD-ROM, and via the Internet.

The future of Macro viruses seems certain, as applications become more and more powerful. Thus, it is vital that we adapt our working environment to protect against them. In a straw poll carried out at the recent FireWalls conference, I asked the audience how many people had even heard of the dangers posed by embedded macros. Less than half those attending raised their hands. This scenario is unfortunately common. Time after time, administrators report they simply have never heard about the Macro viruses. Even more disturbing is the fact that many people admit that while they have heard of the viruses, they have not taken any protective measures, and have no idea whether or not they may have an infected environment.

One of the largest dangers with the Macro viruses is that they are intimately involved with data files. Although the Concept virus did not intentionally damage files on the system, the potential existed. Since then, we have observed other viruses for Word, one of which attempts to modify documents, by adding the following string to the documents, as well as Trojan horses:

And finally I would like to say: STOP ALL FRENCH NUCLEAR TESTING IN THE PACIFIC

Viruses and Hardware Damage

The idea that PC viruses can damage hardware has existed within virus folklore for a very long time. Although there is, as yet, no virus which physically damages a standard PC, there is now a virus which can make it appear that the machine has a damaged hard drive. Once again, this vulnerability was pointed out a long time ago [3], and a solution offered to both MicroSoft and IBM, although curiously, only IBM chose to implement it. (It should be noted that hardware can on occasion be damaged by software, depending upon platform and the precise hardware configuration.)

The virus, known as Rainbow, alters the partition table located in the Master Boot Record of the fixed disk in such a way that, if you attempt to boot from a clean uninfected system disk with MS-DOS 5. x or 6. x, the machine hangs. This is done by creating an extended partition which points back to itself. Thus, when the operating system attempts to view the extended partition, DOS enters an endless loop. This inability to boot the machine from the floppy drive makes it appear rather like a hardware problem [4].

Although this bug is fixed in IBM's PC-DOS, users of MS-DOS must either dabble in a little assembly-language programming, or boot the machine with a version of MS-DOS prior to v3.3.

Viruses and the Internet

Viruses and the Internet is a subject which could fill many volumes. While corporate MIS personnel explore the new vistas offered by the Internet, they can find themselves literally overwhelmed by the amount of information about viruses. The new connectivity increases the familiar problem: Who do you trust? "Experts" need no formal qualifications to dispense viral help. [5] The unwary or uninformed user can just as easily click on a Macro virus infected document as on a photo of his or her favorite vacation spot. To add to the confusion, many users are taking advantage of the public availability of viruses to perform "tests" heedless of the fact that many of the "viruses" are junk [6], and those which aren't pose both a company liability and a danger to their own computers. Not only must we be concerned with all of the expert "help" out there, but also with the intentional distribution of viruses over the Internet which seems to be increasing as quickly as the new challenge of the Internet itself.

Viruses and Anti-virus software

As the number and type of viruses increases, so must the effectiveness of the different types of anti-virus software. As always, determining which is the best product for your site is as tough as ever. Fortunately, there is a move towards developing testing methodology from a number of different sides. The result of this is increased protection for the user community.

One of the biggest developments in testing anti-virus software was the development of the WildList (a list of viruses not found in the laboratory but in the wild, or real world) maintained by Joe Wells [7]. This list accepts contributions from over 35 researchers, including those at companies like Command Software Systems, S& S International PLC and IBM. Thus, the WildList represents a very good snapshot of those viruses which are being reported to virus researchers worldwide. Many testing organizations are now adopting the WildList as the basis for a standard test-set.

Whereas previously, many anti-virus product analyses and reviews centered around a product's ability to detect a large percentage of viruses from a "Zoo" collection (that is, one made up of many thousand different viruses, not necessarily containing viruses which are in the wild.) Newer tests are concerned with the product's ability to stop those viruses which are known to be spreading in the real world. This focusing of testing has dual benefits. First, the user can see at a glance which products are capable of providing adequate detection against the real world threat. In a purely zoo-based test, it would be conceivable for the top-scoring product to be unable to detect the most common virus in the wild. Thus, such test results do not necessarily measure the efficacy of the products.

Second, the focus of the reviewing community on "In the Wild" testing has forced vendors to check and double-check for adequate detection of all viruses known to be in the wild. This results in products that are better able to deal with the real threat, as well as more advanced tests which concentrate on situations users are likely to encounter.

These in the wild criteria are also being applied to all ICSA anti-virus product certifications done after September 1, 1995. This means that products certified under this new scheme should, when run in default mode, be able to detect all those viruses which were known to be spreading a minimum of 2 months before the test date. Full details of the new certification criteria, as well as a list of currently certified products, are given in [8].

Closing Thoughts

The new developments outlined above are only some of the recent events which effect the anti-virus industry. The development of Internet accessibility from the desktop brings with it, its own set of security problems, both virus-related and others. These problems are not likely to disappear with the adoption of Windows 95 and Windows NT. Rather, the potential for viruses, worms and trojans increases. It is not difficult to see how the brave new world envisaged by the system and application designers of today could end up with its own collection of back streets and traps, which will trip up the unwary explorer. More functionality may seem like a good thing, but it is always worth considering how these extra functions might be put to a less than glorious purpose.

As the computing industry develops, there seems little doubt that the virus problem will develop with it. While we can work to design systems which are resilient to the effects of viruses, and educate our children about the wrongfulness of virus writing and distribution, I firmly believe that the virus problem is far from being solved. Although there is no cause for universal uproar, it is equally important that we do not ignore the new risks which are becoming apparent. Information, supplied accurately and without hype, is the only answer.

Endnotes

  1. Dr Harold Highland, "A Macro Virus," Computers & Security, pp. 178-188 (1989).
  2. Sarah Gordon, "What a (WinWord.) Concept," Virus Bulletin, September 1995, pp. 8-9 (1995).
  3. Mike Lambert, "Circular Extended Partitions: Round and Round with DOS," Virus Bulletin, September 1995, pp. 14 (1995).
  4. Jakub Kaminski, "Rainbow: To envy or to hate," Virus Bulletin, September 1995, pp. 12-13. (1995).
  5. Sarah Gordon, "Know your enemy -Threats on the Open Network," Proceedings of the 1995 Information Security Risk Management Symposium, the ALEA Group (1995).
  6. Vesselin Bontchev, "Analysis and Maintenance of a Clean Virus Library," Virus Bulletin Conference Proceedings (1993).
  7. The WildList is a monthly electronic publication maintained by Joe Wells. Archived copies of the WildList are available from ftp. icsa. net.
  8. For a regularly updated list of ICSA-certified products, see http:// www. icsa. net/ avpdcert. html.
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