Why are network sniffers dangerous to an environment?

A.
They can be used to launch active attacks.

B.
Their presence can cause many false positives.

C.
Their presence and activities are not auditable.

D.
They can access sensitive data within applications.

Explanation:
Network sniffers are tools that read network traffic as it passes over
a network interface card (NIC). When attackers use these it is considered a passive
attack because the attacker is not actually doing anything or modifying packets.
Sniffers are not detectable or auditable, thus an administrator would not
necessarily know that one is installed and working within her network.