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If you are active in the anti-virus research field, then you will regularly receive requests for virus samples. Some requests are easy to deal with: they come from fellow-researchers whom you know well, and whom you trust. Using strong encryption, you can send them what they have asked for by almost any medium (including across the Internet) without any real risk.

Other requests come from people you have never heard from before. There are relatively few laws (though some countries do have them) preventing the secure exchange of viruses between consenting individuals, though it is clearly irresponsible for you simply to make viruses available to anyone who asks. Your best response to a request from an unknown person is simply to decline politely.

A third set of requests come from exactly the people you might think would be least likely to want viruses: users of anti-virus software. They want some way of checking that they have deployed their software correctly, or of deliberately generating a "virus incident" in order to test their corporate procedures, or of showing others in the organisation what they would see if they were hit by a virus.

Obviously, there is considerable intellectual justification for testing anti-virus software against real viruses. If you are an anti-virus vendor, then you do this (or should do it!) before every release of your product, in order to ensure that it really works. However, you do not (or should not!) perform your tests in a "real" environment. You use (or should use!) a secure, controlled and independent laboratory environment within which your virus collection is maintained.

Using real viruses for testing in the real world is rather like setting fire to the dustbin in your office to see whether the smoke detector is working. Such a test will give meaningful results, but with unappealing, unacceptable risks.

Since it is unacceptable for you to send out real viruses for test or demonstration purposes, you need a file that can safely be passed around and which is obviously non-viral, but which your anti-virus software will react to as if it were a virus.

If your test file is a program, then it should also produce sensible results if it is executed. Also, because you probably want to avoid shipping a pseudo-viral file along with your anti-virus product, your test file should be short and simple, so that your customers can easily create copies of it for themselves.

The good news is that such a test file already exists. A number of anti-virus researchers have already worked together to produce a file that their (and many other) products "detect" as if it were a virus. Agreeing on one file for such purposes simplifies matters for users: in the past, most vendors had their own pseudo-viral test files which their product would react to, but which other products would ignore.

This test file is known as the "EICAR (European Institute for Computer Anti-virus Research) Standard Anti-Virus Test File", and it satisifies all the criteria listed above. It is safe to pass around, because it is not a virus, and does not include any fragments of viral code. Most products react to it as if it were a virus (though they typically report it with an obvious name: Sophos SWEEP, for example, calls it "EICAR-AV-Test").

The file is a legitimate DOS program, and produces sensible results when run (it prints the message "EICAR-STANDARD-ANTIVIRUS- TEST-FILE"). It is also short and simple -- in fact, it consists entirely of printable ASCII characters, so that it can easily be created with a regular text editor. Any anti-virus product which supports the EICAR test file should "detect" it in any file which starts with the following 68 characters:

X5O!P%@AP[4\PZX54(P^)7CC)7}$EICAR-STANDARD-ANTIVIRUS-TEST-FILE!$H+H*

To keep things simple, the file uses only upper case letters, digits and punctuation marks, and does not include spaces. The only things to watch out for when typing in the test file are that the third character is the capital letter "O", not the digit zero, and that all 68 characters must be on one line, which must be the very first line in the file.

You are encouraged to make use of the EICAR test file. If you are aware of people who are looking for real viruses "for test purposes", bring the test file to their attention. If you are aware of people who are discussing the possiblity of an industry-standard test file, tell them about EICAR.COM, or point them at this article.

If you have a Sophos Anti-Virus CD, you will find a Windows program named SAVTST32.EXE in the \TOOLS\UTILS folder. This handy program can be used to generate a copy of the EICAR test file as required.

About the author

Paul Ducklin joined Sophos from the South African Council for Scientific and Industrial Research in 1995.

He has held a variety of roles within Sophos, including heading up Sophos's global technical support operations, before becoming Head of Technology, Asia Pacific.

One of the world's leading virus experts, Paul has given papers and presentations at various industry events including Virus Bulletin, ICSA and AVAR conferences. He has also written several articles on the virus threat and is a respected industry spokesperson.