yea, frozen armor/health bar is suspicious, but that can be caused by lag, desync etc
other cheaters' 'tricks' can be also not what they look like.
i summarized some thoughts about how to differ cheater from normal players
1. names. cheaters have no chance to become regular players, to make some in-game friends, to build some reputation. so they dont bother picking them proper nicknames.
very often their names look like: ertuj457, 11111111111111, asasasasdas, coaryionpnmz and other pointless letters/digits sets. ofc there are lots of exceptions, but that takes place.
2. behavoir. after getting some skills ppl realise how to move to avoid lead rain around..but sometimes u may see a person who stays still while few other players shoot him. even the newbest of all newbs understands that he has to be fast and unpredictable to avoid bullets. or at least run away...but cheater with his hh's really wont care. so they are always 'cool as shaolin monks'
3. the game routes. as i noticed, cheaters usually choose some crowded place (ship, pd etc) and hang around there, unless they fly in their batmobiles :O. so if the same person is at the same place all the time, and never inside feeding points or ammus, maybe its cheater?
4.no time to talk.cheaters usually dont chat at all, or put in smth in unknown languages and using exotic symbols. the 1st cheater who chatted in english i met today (poor show anyway)
5.turning it on/off. some of them turn on cheats only in case of death threat - person who was running and jumping and loosing hp before, suddenly stops for a second (haxx-on) and becomes impossible to hit. theres definitely cheat-smell around
thats what i dug for now..gotta continue this 'research'
how do u determine that the person was cheater?