Eicar.com - antivirus test file
There are several good reasons for security experts and other to have access to a file that appears to be a malicious program without being so. One such reason may be to test how an antivirus product behaves when finding malicious software.
One such file it eicar.com - a harmless text file consisting of a special string of characters. Nevertheless, by concensus in the antivirus industry, the various antivirus products will alert when this file is scanned, as if it was a real virus.
You can download eicar.com from EICAR's web page (this link opens in a separate browser window).