Table of contentsFirewalls What Are They, What Do They Do, and What Do They Protect Against? Contents Section 1 What Is a Firewall? PowerPoint Presentation What Are Security Policies For? What Does a Packet-Filtering Firewall Do? Services Provided by or in Conjunction with a Firewall Types of Firewalls Firewalls Architectures Screened Host Architecture Screened Subnet Architecture DMZ Between Bastion and Choke Tri-Homed Bastion with DMZ and LAN Section 2 TCP/IP Concepts Underlying a Packet-Filtering Firewall TCP/IP Reference Model IP Information Available to a Stateless Firewall ICMP Packet Header Internet Control Message Protocol Typical ICMP Exchanges UDP Packet Header User Datagram Protocol Typical UDP Exchange TCP Packet Header Transmission Control Protocol TCP Connection Establishment 3-Way Handshake Section 3 Packet-Filtering Concepts Packet-Filtering Firewall Firewall Rules Firewall Rule sets Default Policy Chain List Traversal Deny by Default Policy IFPW Packet Flow Rejecting Versus Denying a Packet Allowing Incoming Packets from only Specific Remote Source Addresses Remote Source Port Filtering Local Destination Port Filtering Filtering Outgoing Packets ICMP Filtering TCP Connection State Filtering Typical TCP Client Rule Pair Section 4 What Do Static Firewalls Protect Against? What Can a Stateless Firewall Protect Against? Source Address Spoofing Importance of Blocking Outgoing Spoofed Source Addresses Probes and Scans General Scan Targeted Scan Scans to Determine OS Type Revealing Useful Information in Response to Port Scans Block Connections to Insecure Services Running on Unprivileged Ports Limit Access to Sensitive or Easily Exploitable Services Malformed Broadcast Addresses Problems with ICMP Network Mapping Source Routed Packets Packet Fragmentation Packet Fragmentation - Teardrop Denial of Service Attacks TCP SYN Flood UDP Flood Smurf Attack (ping) Section Four What a Stateless ipchains Firewall Cannot Protect Against Stealth Scans Slide 62 Applications Using Unusual Protocols FTP Port Mode Data Channel RealAudio / QuickTime Summary |
Author: Robert Ziegler E-mail: rlz@world.std.com Homepage: http://www.linux-firewall-tools.com Further information: |