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.

it consists entirely of printable ASCII characters, so that it can easily be created with a regular text editor. Any anti-virus product that supports the EICAR test file should detect it in any file providing that the file starts with the following 68 characters, and is exactly 68 bytes long:

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

The first 68 characters is the known string. It may be optionally appended by any combination of whitespace characters with the total file length not exceeding 128 characters. The only whitespace characters allowed are the space character, tab, LF, CR, CTRL-Z. To keep things simple the file uses only upper case letters, digits and punctuation marks, and does not include spaces. The only thing to watch out for when typing in the test file is that the third character is the capital letter “O”, not the digit zero.

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 possibility of an industry-standard test file, tell them about www.eicar.org, and point them at this article.