The file is simply a text file of either 68 or 70 bytes that is a legitimate COM file and, when executed, will print "EICAR-STANDARD-ANTIVIRUS-TEST-FILE!" and stop.
The file is simply a text file of either 68 or 70 bytes that is a legitimate executable file called a COM file that can run by Microsoft operating systems and some work-alikes, including OS/2. When executed, will print "EICAR-STANDARD-ANTIVIRUS-TEST-FILE!" and stop.