Any router with a permit or deny, accept, or reject rule set can serve as a firewall. SmoothWall Express, which combines a hardened Linux kernel, intrusion detection, and an IPSec VPN, goes much further than that. It's not as powerful or feature packed as its commercial big brothers from the same company, but it is straightforward to configure and gets the job done. While we're on the subject of firewalls: If you need help with firewall rule sets, take a look at Firewall Builder. It simplifies the configuration of iptables, Cisco PIX and ASA firewalls, and access control lists for other Cisco routers with a GUI front end. FULL REPORT ...