Lyle is a systems security analyst for Gusteffson & Sons, a large law firm in Beverly Hills. Lyle’s responsibilities include network vulnerability scans, Antivirus monitoring, and IDS monitoring. Lyle receives a help desk call from a user in the Accounting department. This user reports that his computer is running very slow all day long and it sometimes gives him an error message that the hard drive is almost full. Lyle runs a scan on the computer with the company antivirus software and finds nothing. Lyle downloads another free antivirus application and scans the computer again. This time a virus is found on the computer.The infected files appear to be Microsoft Office files since they are in the same directory as that software. Lyle does some research and finds that this virus disguises itself as a genuine application on a computer to hide from antivirus software. What type of virus has Lyle found on this computer?

A.
Lyle has discovered a camouflage virus on the computer.

B.
By using the free antivirus software, Lyle has found a tunneling virus on the computer.

C.
This type of virus that Lyle has found is called a cavity virus.

D.
Lyle has found a polymorphic virus on this computer.