Back in 1990-1996 I was involved in anti-virus work for Israeli company and later on for IBM Watson Research building anti-virus technologies and software.

We had a separate, disconnected laboratory with strict rules (disk-in / no disk out!). Nasty unknown stuff being tested there.

At some time my work was to develop virtual machine (in C) capable of emulating x86 instruction set to quickly run EXEc files through it to detect if anything weird was going on.

Fun times!