These new services will be in high demand and will often require either firewall exemptions for specific users or general reconfigurations to permit this new and relatively untested software to function. Another issue with newer technologies is that the line between data and programs continues to blur with each passing year. Macro programming in Word and its associated viruses and Java-enabled Web browsers are good examples of situations where a firewall would have extremely limited ability to offer protection. Another general issue is with the concept of placing so many of your security eggs in the single basket of a firewall. Even if a firewall is installed, it is still absolutely critical to maintain the best possible security on all of the computer systems on the protected network.
Firewalls are subject to attack and can be compromised.
Even with a firewall, it is still absolutely critical that all of the systems on the network are properly configured to resist attack.