The Antwerp Diamond Center vault is 2 stories underground and protected by 10 layers of security. It was thought to be impregnable.
Wired magazine has a fascinating behind the scenes account of the robbery. The details are provided by one of the criminals later caught and convicted.
A security camera recorded his movements—police would later watch the footage—but the guard had gotten used to the Italian’s frequent visits and wasn’t paying attention. Notarbartolo stepped away from the safe-deposit boxes and pulled out the aerosol can. With a quick, practiced circular movement, he covered the combined heat/motion sensor with a thin coat of transparent, oily mist.
The vault was momentarily filled with the smell of a woman’s hair.
It was a simple but effective hack: The oily film would temporarily insulate the sensor from fluctuations in the room’s temperature, and the alarm went off only if it sensed both heat and motion.
Still, it was hard to guess how long the trick would work. Once the Monster was in the vault, he had to install the sensor bypass before his body heat penetrated the film. He might have five minutes—he might have less. Nobody knew for sure.