Uplink (2001) is one of my favourite hacking games. The first game made by Introversion Software ("The last of the bedroom programmers, the first of the children"), it is considered widely influential in the hacking game space.

NOTES:

1. I am using a custom theme because the default one is too blue for my liking.
2. Music and SFX are enabled.
3. I recommend playing it at 800x600 resolution as the UI scales pretty poorly at larger resolutions. The game is recorded at 1920x1080 since that is a very crisp result, but it's not as fun to play when the icons are so tiny.