Network Attacks and Defenses

Packet Filtering and Inspection  ◾  201

configuration error, while generalization and correlation are,

in fact, often used by firewall administrators to make a rule

set compact. Nevertheless, it may be the case that some of the

generalizations and correlations are not intentional, in which

case it is useful to detect them and let the administrator decide

whether or not they are harmful. Redundancy is not consid-

ered a serious configuration error either, but redundant rules

are clearly useless; therefore, it is worth identifying and remov-

ing them and increasing the efficiency of filtering by doing so.

7.4.3 Importance of the Filtering Rules Ord