Are you old enough to Remember Uplink?
It was probably (and still is) the best/most famous "90s hacking simulator".
Well, the original creators apparently made a mod-overhaul to make the game look "modern" (it's still a 15 years old title after all), with minor gameplay upgrades.
The original installer was 16bit -while the game is 32-, so pirated version won't even install on newer machines (without using specific tools);
Legit version is currently around 1.40$ on Steam, it's in sale
Here's the new mod: http://www.moddb.com/mods/uplink-os