How does a denial-of-service attack work?


A. A hacker prevents a legitimate user (or group of users) from accessing a service
B. A hacker uses every character, word, or letter he or she can think of to defeat authentication
C. A hacker tries to decipher a password by using a system, which subsequently crashes the network
D. A hacker attempts to imitate a legitimate user by confusing a computer or even another person