Linux Firewalls

by Ziegler, Robert L.

• ISBN13: 9780735709003
• ISBN10: 0735709009
• Format: Paperback
• Copyright: 1999-11-01
• Publisher: Pearson P T R

Summary

With the explosion of Linux on both college campuses and in corporate environments, any marketable CS student will need Linux skills in his bag. In addition to guiding students through the basic steps of designing and implementing a packet-filtering firewall, Linux Firewalls discusses disabling unnecessary services, selecting services to make public, and identifying dangerous local services that need to be protected behind a firewall. Students will find information on higher-level forms of access control, common server configuration issues, and system security and integrity monitoring. They will gain skills to detect preliminary probes and unauthorized access attempts before an intrusion occurs. Ideal of both security and system administration courses.

Author Biography

Robert L. Ziegler is now a principal engineer with Nokia.

Table of Contents

Introduction	xv
I Preliminary Considerations	1	(16)
Preliminary Concepts Underlying Packet-Filtering Firewalls	3	(14)
The TCP/IP Reference Networking Model	4	(3)
Service Pots: The Door to the Programs on Your System	7	(2)
Packets:IP Network Messages	9	(7)
Summary	16	(1)
II Packet-Filtering and Basic Security Measures	17	(236)
Packet-Filtering Concepts	19	(42)
A Packet-Filtering Firewall	20	(3)
Choosing a Default Packet-Filtering Policy	23	(2)
Rejecting Versus Denying a Packet	25	(1)
Filtering Incoming Packets	26	(12)
Filtering Outgoing Packets	38	(2)
Private Versus Public Network Services	40	(19)
Summary	59	(2)
Building and Installing a Firewall	61	(66)
ipchains: The Linux Firewall Administration Program	62	(5)
Initializing the Firewall	67	(8)
Filtering ICMP Control and Status Messages	75	(5)
Protecting Services on Assigned Unprivileged Ports	80	(5)
Enabling Basic, Required Internet Services	85	(7)
Enabling Common TCP Services	92	(22)
Enabling Common UDP Services	114	(5)
Logging Denied Incoming Packets	119	(2)
Denying Access to Problem Sites Up Front	121	(1)
Enabling LAN Access	122	(2)
Installing the Firewall	124	(2)
Summary	126	(1)
LAN Issues, Multiple Firewalls, and Perimeter Networks	127	(104)
LAN Security Issues	129	(1)
Configuration Options for a Trusted Home LAN	129	(4)
Configuration Option for a Larger or Less Trusted LAN	133	(13)
A Formal Screened-Subnet Firewall	146	(83)
Summary	229	(2)
Debugging the Firewall Rules	231	(22)
General Firewall Development Tips	232	(1)
Listing the Firewall Rules	233	(6)
Checking the Input, Output, and Forwarding Rules	239	(5)
Testing an Individual Packet Against the Firewall Rules	244	(2)
Checking for Open Ports	246	(4)
Debugging SSH---A Real-Life Example	250	(2)
Summary	252	(1)
System Level Security and Monitoring	253	(88)
Verifying that the System Is Running as You Expect	255	(18)
Checking the Network Interfaces with ifconfig	255	(2)
Checking the Network Connection with ping	257	(1)
Checking Netwok Processes with netstat	258	(1)
Checking All Processes with ps -ax	259	(3)
Interpreting the System Logs	262	(9)
Summary	271	(2)
Issues At the UNIX System Administration Level	273	(52)
Authentication: Verifying Identity	273	(3)
Authorization: Defining Access Rights to Identities	276	(6)
Server-Specific Configuration	282	(36)
SOCKS: An Application-Level Proxy Firewall	318	(2)
Miscellaneous System Accounts in /etc/passwd and /etc/group	320	(1)
Setting Your PATH Variable	321	(1)
/etc/issue.net	322	(1)
Remote Logging	322	(1)
Keeping Current With Software Upgrades	323	(1)
Summary	324	(1)
Intrusion Detection and Incident Reporting	325	(16)
System-Int egrity Checkers	326	(2)
Symptoms Suggesting That the System Might be Compromised	328	(4)
What To Do If Your System Is Compromised	332	(1)
Incident Reporitng	333	(6)
Summary	339	(2)
Appendixes	341	(106)
Security Resources	343	(8)
Information Sources	343	(1)
Software Collections	344	(1)
Security Tools	345	(1)
Firewall Tools	346	(1)
Reference Papers and FAQs	347	(2)
Online Documentation	349	(1)
General Web Sites	349	(1)
Books	350	(1)
Firewall Examples and Support Scripts	351	(82)
ipchains rc.firewall for an Individual System or Home LAN from Chapter 3	352	(19)
ipfwadm rc.firewall for an Individual System or Home LAN from Chapter 3	371	(19)
Optimizing the Firewall Rules	390	(32)
Special-Purpose Support Scripts	422	(3)
DHCP: Firewall Support with a Dynamic IP Address and Name Servers	425	(8)
Glossary	433	(14)
Index	447