Biochip
Biochips were a type of Borg technology implanted in the brain. A Borg drone would die if the biochip implants were removed permanently due to their brains growing dependent upon them.

Jean-Luc Picard suggested introducing an invasive program through the biochip system of Third of Five to send a virus back to the hive. Geordi La Forge told the drone that Dr. Crusher had repaired damage to its biochip implants, but that tests would need to be run to verify that things were working properly. Data and La Forge came up with a paradoxical geometrical image to implant in the system, and noted that Hugh would attempt to analyze it, but be unsuccessful. It would then be stored in his memory banks and shunted to a subroutine for further analysis. ()

Borg components