Since Steam's launch process and DayZ_BE.exe run the game (DayZ.exe) with Administrator access (in my case), DayZ.exe becomes relevant.

BattleEye client was already installed by version 0.58 as a necessity for nearly all servers. Having the BattleEye client running as a service means that Administrator level access is not only required for installation, but that it is (by design) monitoring users' computers beyond the scope of the game while interacting with a game's process(es) and possibly being affected directly by the game (and anything else that is aware of the service). Meanwhile, only other services and kernel level objects (such as rootkits) have a chance at interfering with any changes the service decides to make or it actions it takes.