QAZ
QAZ is a network worm. The worm disguises itself as Notepad.exe and spreads by scanning for shared drives on the network, which increases network traffic. It also reportedly sends the IP address of the infected machine back to the creator of the worm, who can then gain access to the computer through the worm.

Qchain
Qchain is a tool from Microsoft Corporation to simplify the task of installing multiple hot-fixes.

QFE: Quick Fix Engineering
Quick Fix Engineering is a Microsoft team that produces critical updates for a product, and by extension the name of the updates themselves.

Qfecheck
Qfecheck is a tool from Microsoft for enumerating installed hot-fixes on a system.

Quantum Cryptography
In quantum cryptography, the information is protected by the laws of quantum physics such as Heisenberg's Uncertainty Principle and quantum entanglement. Quantum cryptography provides the means for two parties to exchange an enciphering key over a private channel. The traditional cryptography employs various mathematical techniques to encrypt the content of messages.

Quarantine Area
In anti-virus programs, Quarantine Area is the holding area to which suspicious or infected files are moved so that they are unavailable to the user, but not lost forever. This allows users organisations to remove infected files from general circulation without deleting them permanently.

Queso
Queso is a tool to detect what OS a remote host is running with a pretty good degree of accuracy, by using a variety of valid and invalid tcp packets to probe the remote host it checks the response against a list of known responses for various operating systems