SHD
Currently, the only knowledge of the SHD group comes from various radio broadcasts heard around Malton, from broadcasters with a history for discussing conspiracy theories (in addition to random broadcasts about PKers and GKers who may or may not be actual PKers or GKers). While impossible to verify the accuracy of each of their claims, recurring themes of government overreach and secret agents have appeared several times.
From a broadcast heard during August 2017:
"Now everyone knows about survivor groups, right? The revivers, doctors, the people who hunt GKers and PKers, zombie hunters, doing what they can to keep some semblance of civic order. Keeping things from falling totally into crap. Nothing but respect for those folks. Those are the people in your neighborhood, they're us. But, they ain't the only ones out there. You ever hear of a little thing called the National Security and Homeland Security Presidential Directive? No? You wouldn't have. Not the sort of thing they put on the front page of 'The Post.' No, the directive is more of your basic 'secret government take over plan' type deal, to provide what the spooks refer to as 'continuity of government.' Doesn't sound so scary does it, until you find out how it works. Which is, they got clandestine government agents embedded among us. And when the directive goes out, those agents get activated. Our government has sleeper cells in our own goddamn country. NSA types who look and sound like you and me, until their “on” switch gets flipped. And then what? They start rounding people up, putting them in camps, executing us? I don't know, but the thing is, nobody knows. I mean, martial law is undemocratic, but at least it's transparent. Who these people are, what they're up to, it's all so top secret that even the president probably doesn't know the details. Plausible deniability folks. Home of the free, my ass."
With no real noticeable group activity, in addition to only being mentioned by unverifiable radio broadcasts, the existence of this group is mostly speculation, as they may not even exist.