BD-1 gains the ability to hack probe droids, but he can also learn how to hack the large security droids in Jedi: Fallen Order. To grab this piece of technology, you’re going to need to visit Kashyyyk to find it.
Here is the location of the Security Droid hack upgrade for BD-1.
It’s in the Imperial Refinery. You’re going to need to go the right, swinging on two vines to get to it.
When you acquire the upgrade, find a security droid to test it on with BD-1. Unlike the probe droids, though, you cannot immediately hack them. You need to damage it a good portion of their health. When they’re almost defeated, they’re going to short circuit for a few seconds and pause.
This moment is when you can hack them. Hit down on the directional pad to begin hacking them, and let BD-1 do his thing. After it’s hacked, the droids are going to gain a portion of their health back and start fighting on your behalf.
If you have a few stormtroopers still alive near the security droid, it can easily take them out. You can receive the achievement called Don’t Mess with BD-1.