The EICAR test file was given a shiny new coat of paint this September (2006). Nothing inside the file changed, but the file is no longer "The Anti-virus test file", it is now "The Anti-Virus or ...

EICAR (formerly known as the European Institute for Computer Anti-virus Research, though that title hasn't been used for a good while) is best known for its yearly conference and for the EICAR test ...

is a harmless text file that is detected as a virus by most AV vendors. You can use it to verify that your local virus scanner is working (just copy the string into a plain text file), check to see if ...