Creating which of the following is how a hacker can insure his ability to return to the hacked system
at will?

A.
rootsec

B.
checksum

C.
CRC

D.
backdoors

E.
None of the choices.

Explanation:
A backdoor refers to a generally undocumented means of getting into a system, mostly for
programming and maintenance/troubleshooting needs. Most real world programs have backdoors.
Creating backdoors is how a hacker can insure his ability to return to the hacked system at will.