What tool is being used to determine whether attackers have altered system files of executables?

What tool is being used to determine whether attackers have altered system files of executables?

A.
File Integrity Checker

B.
Vulnerability Analysis Systems

C.
Honey Pots

D.
Padded Cells

Explanation:
Although File Integrity Checkers are most often used to determine whether attackers
have altered system files or executables, they can also help determine whether
vendor-supplied bug patches or other desired changes have been applied to system
binaries. They are extremely valuable to those conducting a forensic examination of
systems that have been attacked, as they allow quick and reliable diagnosis of the
footprint of an attack. This enables system managers to optimize the restoration of
service after incidents occur.