What is the ruling on a woman covering her hair in places where phones might be hacked and cameras might expose what is inside the home?

Hacking is an illicit way to achieve a goal, and it falls under forbidden espionage, as Allah Almighty says: "And do not spy." Opening others' phone cameras through hacking is considered forbidden espionage. You are not required to wear the niqab in front of mahrams and women due to the possibility of cameras being hacked, because this assumption is weak and should not be given attention. The basic principle is that rulings are built upon knowledge, and doubt is not considered. The default is that cameras are safe from hacking simply by looking, and this is a weak possibility upon which no ruling can be based. Permission to enter was granted for the sake of vision, and the Lawgiver did not demand precaution by wearing hijab (definition) inside homes out of fear of espionage.