While hacking various machines for Master Hacker you will need to hack the security bots and turrets. Hack one of these robots and allow them to kill for you. A little patience is required as you will have to let the security bots kill your enemies.
Using security Plasmids or Security Cameras doesn't count towards the achievement. You need to directly hack a turret or bot for your kills to count.
If you are having issue finding bots and turrets allow the security cameras to raise the alarm so you can hack the bots.