The 1989 malware widely regarded as the first ransomware was the AIDS Trojan.
The program was distributed on floppy disks labeled “AIDS Information,” which were mailed to researchers and attendees of a World Health Organization conference. After a set number of reboots, it hid file names and encrypted the names of files on the computer, then displayed a ransom demand.
The malware was created by Joseph L. Popp, an evolutionary biologist who was arrested after investigators traced the disks. The demanded payment was to be mailed to a post office box in Panama. The AIDS Trojan did not use modern cryptographic ransomware techniques, but its extortion model established the basic pattern later used by much more damaging attacks.
It is sometimes called the PC Cyborg Trojan, after the name shown in its ransom message. The terms “virus” and “ransomware” are often used loosely for it, but ransomware is the more precise description because it withheld access until payment was requested.