An air gap is a way to physically isolate a computer or other connectable devices from the internet. The name describes the literal physical gap of air between the computer and the internet, assuming that its wireless connection is either non-existent or turned off. By not being connected to the internet, one of the biggest attack surfaces is immediately nullified.
Although air gaps are known to be a useful way to provide additional security, there are not unbreachable, since in many cases it is still likely that the unconnected computer is likely to receive files from a removable media source. Stuxnet is an example of a malware which was able to breach the air gap in this way.
Last updated: 5 September 2017