Includes index.

Packet-Filtering and Basic Security Measures -- Preliminary Concepts Underlying Packet-Filtering Firewalls -- The TCP/IP Reference Networking Model -- IP Addresses -- Routing: Getting a Packet from Here to There -- Service Ports: The Door to the Programs on Your System -- Packets: IP Network Messages -- Packet-Filtering Concepts -- A Packet-Filtering Firewall -- Choosing a Default Packet-Filtering Policy -- Rejecting Versus Denying a Packet -- Filtering Incoming Packets -- Filtering Outgoing Packets -- Private versus Public Network Services -- ptables: The Linux Firewall Administration Program -- Differences Between IPFW and Netfilter Firewall Mechanisms -- iptables Features -- iptables Syntax -- Building and Installing a Standalone Firewall -- iptables: The Linux Firewall Administration Program -- Initializing the Firewall -- Protecting Services on Assigned Unprivileged Ports -- Enabling Basic, Required Internet Services -- Enabling Common TCP Services -- Enabling Common UDP Services -- Filtering ICMP Control and Status Messages -- Logging Dropped Incoming Packets -- Logging Dropped Outgoing Packets -- Denying Access to Problem Sites Up Front -- Installing the Firewall -- Advanced Issues, Multiple Firewalls, and Perimeter Networks -- Firewall Optimization -- Rule Organization -- User-Defined Chains -- Optimized Example -- What Did Optimization Buy? -- Packet Forwarding -- The Limitations of a Standalone Firewall -- Basic Gateway Firewall Setups -- LAN Security Issues -- Configuration Options for a Trusted Home LAN -- Configuration Options for a Larger or Less Trusted LAN -- A Formal Screened-Subnet Firewall -- Converting the Gateway from Local Services to Forwarding -- NAT--Network Address Translation -- The Conceptual Background of NAT -- iptables NAT Semantics -- Examples of SNAT and Private LANs -- Examples of DNAT, LANs, and Proxies -- Debugging the Firewall Rules -- General Firewall-Development Tips -- Listing the Firewall Rules -- Checking the Input, Output, and Forwarding Rules -- Checking for Open Ports -- Debugging SSH: A Real-Life Example -- System-Level Security and Monitoring -- Verifying That the System Is Running as You Expect -- Checking the Network Interfaces with ifconfig -- Checking the Network Connection with ping -- Checking Network Processes with netstat -- Checking a Process Bound to a Particular Port with fuser -- Checking All Processes with ps -ax -- Interpreting the System Logs -- Issues at the UNIX System Administration Level -- Authentication: Verifying Identity -- Authorization: Defining Access Rights to Identities -- Server-Specific Configuration -- SOCKS: An Application-Level Proxy Firewall -- Miscellaneous System Accounts in /etc/passwd, /etc/shadow, and /etc/group -- Setting Your PATHVariable -- /etc/issue.net -- Remote Logging -- Keeping Current with Software Upgrades -- Secure Shell (SSH) -- Installing SSH -- Generating SSH Keys -- Using SSH -- Customizing Your SSH Configuration -- Secure Copy (scp) -- Tripwire -- Installing Tripwire -- Looking at How Tripwire Works -- Configuring Tripwire -- Intrusion Detection and Incident Reporting Software -- Intrusion-Detection Software -- Symptoms Suggesting That the System Might Be Compromised -- What to Do if Your System Is Compromised -- Incident Reporting -- Security Resources -- Security Information Sources -- Software Collections -- Security Tools -- Firewall Tools -- Firewall Examples and Support Scripts -- iptables Firewall for a Standalone System from Chapter 4 -- Optimized iptables Firewall from Chapter 5 -- iptables Firewall for a Choke Firewall from Chapter 6 -- Special Purpose Support Scripts -- DHCP and pump: Firewall Support with a Dynamic IP Address and Name Servers -- VPN -- Overview of Virtual Private Networks (VPN) -- Types ofVPN -- VPN Protocols -- Linux and VPN Products -- VPN Configurations -- Connecting Networks -- VPN and Firewalls.

Updating the highly successful first edition to cover the Linux 2.4 kernel. Author Ziegler is a router security architect who is well respected in the Open Source community as a firewall expert. Includes extensive coverage of iptables, the biggest additional change to the 2.4 kernel.