Contrary to what is shown in films, being a spy is not all that glamorous and easy. It also involves taking extreme measures so as not to be discovered by the enemy. This includes disguises.
The former Chief of Disguise of the Central Intelligence Agency (CIA), Jonna Mendez, explained (video above) how exactly the organisation approached the use of disguises to hide an agent’s identity. On an episode of Wired’s Masterminds, Mendez explained that disguise could be as simple as wearing a wig or glasses for brief meetings, or be advanced enough to work for extended periods of time.
“The goal is that if someone were to write a memo describing you, every item on that memo would be wrong,” Mendez said. She also talked about the other aspects that a person would have change – like behavioural traits – that would make the facade more convincing.