When he ran it on his air-gapped vintage PC, there was no flashy intro. Instead, a terminal window flickered to life.
Leo froze. The vintage PC wasn't connected to the internet. It couldn't see his laptop. infect.exe
Unlike a standalone Trojan, a file infector modifies existing programs. When you run the "clean" program, the virus code executes first, often looking for other files to "infect" before handing control back to the original application. Historical Examples: When he ran it on his air-gapped vintage