StackGuard (as used by Immunix), ssp/ProPolice (as used by OpenBSD), and Microsoft’s /GS
option use _____ defense against buffer overflow attacks.

A.
Canary

B.
Hex editing

C.
Format checking

D.
Non-executing stack

Explanation:
Canaries or canary words are known values that are placed between a buffer and
control data on the stack to monitor buffer overflows. When the buffer overflows,it will clobber the

canary,making the overflow evident. This is a reference to the historic practice of using canaries in
coal mines,since they would be affected by toxic gases earlier than the miners,thus providing a
biological warning system.