Department of Redundancy Department specializes in multi-layer security. I suspected that they might have inserted a backdoor into some of their products, so I checked out their own systems. They've protected themselves with a lot of layers, but thankfully, it looks like most of those layers are the same. It shouldn't be too hard to bypass all of them after the first one.
Woah... this is some tricky stuff. They've got narrow access windows set up there; that sort of strict timestamping would never hold up in a high-uptime system that had to deal with internet-level latency. These backdoors must just be for local access, and their tolerances are just barely broad enough to allow external exploitation.
These systems... I want to talk about them, but they're too interesting to ruin the exploration... oh! *installs spoiler plugin*
I'm thinking that the DRD is using genetic algorithms ( http://en.wikipedia.org/wiki/Genetic_algorithm ) or neural nets to design their security. That's the only explanation for how they have so many different layers that are similar-looking but very different in practice. It seems especially likely given that some of the systems seem to have unused components; a manually-designed system wouldn't demonstrate those "vestigial" things. So. Awesome.