The most likely error to occur when implementing a firewall is:

A. incorrectly configuring the access lists.

B. compromising the passwords due to social engineering.

C. connecting a modem to the computers in the network.

D. inadequately protecting the network and server from virus attacks.

Explanation:

An updated and flawless access list is a significant challenge and, therefore, has the greatest chance for errors at the time of the initial installation. Passwords do not apply to firewalls, a modem bypasses a firewall and a virus attack is not an element in implementing a firewall.