If Cobras are operating at high altitude, they can be easilly targetted by SAMs.
I remember, i hav read in Newsweek, account of US Iraqi veteran pilot, in which, he describes flying over hostile areas. The trick to avoid SAMs and of course Small Arms fire is to Fly Low and Fly Fast. So both types of threats can be , to some extent defeated.
Cobra is a dedicated attack helicopter ( not to be considerred as commercial aircraft). Its structure and surface skin is designed to take 7.62 mm rounds. Vital parts of the chopper (Pilot,gunner compartment; engine, mainn transmission system) is protected by Kevlar sheets, which can take 12.7 mm rounds and still fly. Its has dual flight controll system. So if one system fails, the other will take over, and will give pilot enough time to dash back to safety.
Flying at high altitude, the aircraft loses element of surprise and stealth, which are, actually the characteristics of attack helicopter.