If you're planning on taking the Security+ exam, you should understand malware such as CryptoLocker and the Police Virus.
For example, can you answer this sample Security+ practice test question?
Q. After Maggie turned on her computer, she saw a message indicating that unless she made a payment, her hard drive would be formatted. What does this indicate?
A. Armored virus
Check out this post to see the answer and explanation.