So, this is where the main bulk of it is. The good gear can determine winning or losing that hack.
Rundown:
Explosive shotguns are amazing, make sure the DPS is about 250 or higher otherwise you risk not enough damage. I'd say, get 2 of these as they can be amazing, 1 for L-Click. And the other on 1-5.
Slowing Shotguns or Freezing Shotguns, get 1 but make sure dps is above 300 and has about 12 projectiles (Get Double Data Rate as its incredibly useful.)
EMP. I can't stress how good these are, they stun the enemys or slow them to a snails pace! Just get 1 though.
Insta Heals and Healing Over Time are god like here, So get amazing ones.
Reccomended add ons.
Damage Reduced, Get ALOT,
Extra HP. Really good, especially with them doing what like 800 damage at level 50?
Movement Speed, you'll know why later on when we get to the stratedgy itself.
Hack Time Reduced, this is good so you dont spend 3 mins in the hack itself.
Lets move on shall we?

So, once you've started the hack at the information panel, drop to the floor below it and start running around the corners, shooting your freeze or slowing shotgun. Once EMP and both Explosive Shotguns are ready, stun then use all 3 of your shotguns at once, causing mass damage. If on low HP, heal with your instant heal as fast as you can. The 2nd layer isnt the floor but the one above the floor, to let you know. Rinse and Repeat.