To Firewall or not to Firewall – Trusted & Untrusted Networks
The big danger of firewall deployments within a complex dynamic network infrastructure (a typical enterprise) is you end up with placebo network security. It is a problem that creeps in with each firewall rule change over the course of time. No one ever seems to be concerned when adding a new rule to a firewall ruleset, but removing a rule is a fearful business, so often it is not risked, so not to break anything. The g eneral adhoc adding of rules without first understanding the entire ruleset is what seriously weakens firewall security, it makes rulesets hard to understand and can mushroom into an ineffective firewall configuration. So instead of allowing a network range through on specific set of ports as a single rule, you end up with tens of rules allowing individual IPs each on a specific port. I have seen firewall rulesets with thousands of unnecessary individual rules, caused by a combination of poor firewall management, lack of change control...