Which type of attack can use a worm or packet sniffer to crash systems, causing low resources and/or consuming bandwidth?

A.
Denial-of-service attack

B.
Illicit server attack

C.
Man-in-the-middle attack

D.
Virus attack

Explanation:
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A denial of service attack (DoS) is when a hacker causes access to a server, network, or other resource to be denied. One common method of DoS is to crash the network components so that network connectivity is lost. Another method is to flood the server or network with excessive traffic so that no one else can get in and access that sever or network. In order to do that, resources have to be depleted, or all of the bandwidth taken up. The bottom line is to consume most, if not all, of the resources so that other users, legitimate users, are locked out.
Incorrect Answers:
B: An illicit server attack utilizes an unauthorized service or daemon running on your system to send out information to a hacker that can be used to further compromise the system.
C: A man-in-the-middle attack is also when someone gets in the middle of a transaction between two servers and intercepts the transaction flow. This differs slightly from the hijacking attack. In the hijacking attack the man-in-the-middle actually cuts in and impersonates one the partners, but in a man-in-the-middle attack, the intervening party only eavesdrops and listens to the stream.
D: A virus is a type of attack that uses a simple or complex program that self-replicates and/or deposits a payload on a remote or local computer