X5O!P%@AP[4\PZX54(P^)7CC)7}$EICAR-STANDARD-ANTIVIRUS-TEST-FILE!$H+H*
Fun fact: This is a valid 16-bit x86 executable, written solely using printable ASCII. To avoid unprintable characters, it uses self-modifying code (XOR and AND) to patch itself in RAM. https://blog.nintechnet.com/anatomy-of-the-eicar-antivirus-test-file/ #retrocomputing