The EICAR test file (official name: EICAR Standard Anti-Virus Test File) is a file, developed by the European Institute for Computer Antivirus Research, to test the response of computer antivirus (AV) programs. The rationale behind it is to allow people, companies, and AV programmers to test their software without having to use a real computer virus that could cause actual damage should the AV not respond correctly. EICAR likens the use of a live virus to test AV software to setting a fire in a trashcan to test a fire alarm, and promotes the EICAR test file as a safe alternative.

A compliant virus scanner, when detecting the file, will respond in exactly the same manner as if it found genuinely harmful code. Its use can be more versatile than straightforward detection – for example, a file containing the EICAR test string can be compressed or archived, and then the antivirus software can be run to see whether it can detect the test string in the compressed file.The Eicar test string reads:

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

It can be created by using notepad and save as .com extension. Or download via Website of EICAR.

Notes:

* The third character in the string is the capital letter O, not a zero.
* Although the string itself is 68 bytes in length, some text editors add an extra blank line (CR+LF) to the end of the file, increasing the size to 70 bytes. This does not affect its functionality.