There is almost certainly no way to bring back most people who have died. With the destruction of their brains, the information that makes up their memory is probably nowhere we can retrieve it. Maybe for example something different is happening in a worm's digestive system because it ate through a memory that was one way instead of another. But that's shortly after the brain is eaten by the worm (and other stuff). You'd have to capture the worm and take it apart impossibly delicately to even have a chance of getting the information back. You'd have to have enough information about the prior state of the worm and its surroundings to know how the insides of the worm would be different depending on the state of the memory before it being eaten. The things you would have to know to track down each bit of information explode outward as more things happen to the worm and its surroundings, etc. I'm pretty sure this is something not even a superintelligence could do.

It might be possible to bring back a little bit of someone who has been dead short enough that they still have lots living friends, acquaintances, and detailed records of things related to their thoughts. Though there should be lots of little hidden internal details that can't be inferred from their external behavior, which couldn't be reconstructed.

There's also cryonics, though it can't help most people who are already dead and probably won't be able to help most people who have yet to die.