What Is a Denial of Service Attack

Multiple Choice

What is a denial of service attack?

A) A denial of service attack occurs when the perpetrator sends hundreds of messages from randomly generated false addresses, overloading an Internet service provider's e-mail server.
B) A denial of service attack occurs when an e-mail message is sent through a re-mailer, who removes the message headers making the message anonymous, then resends the message to selected addresses.
C) A denial of service attack occurs when a cracker enters a system through an idle modem, captures the PC attached to the modem, and then gains access to the network to which it is connected.
D) A denial of service attack occurs when the perpetrator e-mails the same message to everyone on one or more Usenet newsgroups LISTSERV lists.