Dead hand works off what is at heart a very simple set of passive sensors (seismographs and pressure sensors etc) and doesn't itself have any active targeting systems. The missiles already have their pre-set targets uploaded prior to launch and the system can't alter those (apparently). It also has no active tracking capability. This means its not a good analogy for the type of system you want.
That would require a much more sophisticated set of sensors including satellite imaging and radio location. This is because Dead Hand's system operates inside the national boundaries of Russia. So unless this system has been designed to hit domestic targets (!) it needs some means of detecting activity far away in areas its former masters didn't control. Seismographs would still help but I doubt it would be enough.
The short answer would be to cripple those sensors. Blind it (or at least make it extremely myopic) However that in turn depends on one big unanswered question about your scenario.
What do the rescue teams/survivors know about the system? What technical specifics do they have. Where is the system located, how many launch systems does it have at its disposal and what type, where are they located, what type of sensors does it use and where are they located.
For a start is it even on the same continent as the one where your survivors want to start rebuilding?
Without any of that information its kind of hard to come up with a definitive solution other than to try and wait it out. That said complex electronics run 24/7 need down time and maintenance no matter how many back-ups you install. For that matter cruise missiles (if that is the type of weapon being used) need maintenance to. I have no idea what the maintenance schedule for kind of platform would be but I doubt it could be left sitting around for say 20 years without turning into a 'fizzer' if it was launched.
Even the nuclear warheads have a limited lifespan due to radioactive decay, especially if thermonuclear - the tritium has a half-life of 12.5 years. They don't just need maintenance, they need replacement.
If you want better options. Provide more details.
EDIT; You also need to define what you mean by 'large concentrations' of people and equipment. How many is large? 1000 plus people and entire reconstruction convoy? 6 guys in a camper van? Because if the setting is at the upper end of some scale survivors might (through trial and error figure out that rebuilding programs under a certain size are 'safe' and therefore until the system breaks down they just rebuild 'small and dispersed'. (Albeit that might be a hard earned lesson.)