Generally speaking, modern computer viruses have one purpose: Making money for some nefarious actor, whether it’s by turning infected machines into link-clicking bots or demanding a ransom to free up a seized device. But there was a time — the mid-1990’s — when viruses were more like pranks, spread via infected floppy disks instead of the Internet.
Above, check out what it looked like when a computer was infected with some of the earliest viruses. “Then, malware writers were writing PC viruses just as a hobby,” says Finnish computer security expert Mikko Hyppönen, who provided the images to TIME. “They weren’t trying to make money with the malware, they weren’t trying to become famous. Their main motive was to do it just because they could, or to prank their victims.”