Guide to Firewalls and Network Security with Intrusion Detection and ...

slurpslapoutNetworking and Communications

Nov 20, 2013 (4 years and 5 months ago)


Ongoing Administration

Chapter 11

Learning Objectives

Learn how to evolve a firewall to meet new
needs and threats

Adhere to proven security principles to help
the firewall protect network resources

Use a remote management interface

Track log files for security


Learning Objectives

Follow basic initial steps in responding to
security incidents

Take advanced firewall functions into
account when administering a firewall

Making Your Firewall Meet New






Verifying Resources Needed by
the Firewall

Ways to track memory and system

Use the formula:

MemoryUsage = ((ConcurrentConnections)/
(AverageLifetime))*(AverageLifetime + 50

Use software’s own monitoring feature

Verifying Resources Needed by
the Firewall

Allocating More Memory

Identifying New Risks

Monitor activities and review log files

Check Web sites to keep informed of latest
dangers; install patches and updates

Adding Software Updates and

Test updates and patches as soon as you
install them

Ask vendors (of firewall, VPN appliance,
routers, etc) for notification when security
patches are available

Check manufacturer’s Web site for security
patches and software updates

Using an Automated Update

Obtaining Updates from the
Vendor’s Web Site

Adding Hardware

Identify network hardware so firewall can
include it in routing and protection services

Different ways for different firewalls

List workstations, routers, VPN appliances,
and other gateways you add as the network

Choose good passwords that you guard

Dealing with Complexity on the

Distributed firewalls

Installed at endpoints of the network, including remote
computers that connect to network through VPNs

Add complexity

Require that you install and/or maintain a variety of firewalls
located on your network and in remote locations

Add security

Protect network from viruses or other attacks that can originate
from machines that use VPNs to connect (eg, remote laptops)

Dealing with Complexity on the

Adhering to Proven Security

Generally Accepted System Security
Principles (GASSP) apply to ongoing
firewall management

Secure physical environment where firewall
related equipment is housed

Importance of locking software so that
unauthorized users cannot access it

Environmental Management

Measures taken to reduce risks to physical
environment where resources are stored

up power systems overcome power outages

up hardware and software help recover network
data and services in case of equipment failure

Sprinkler/alarm systems reduce damage from fire

Locks guard against theft

BIOS, Boot, and Screen Locks

BIOS and boot
up passwords

Supervisor passwords

Screen saver passwords

Using Remote Management

Software that enables you to configure and
monitor firewall(s) that are located on
different network locations

Used to start/stop the firewall or change
rulebase from locations other than the
primary computer

Why Remote Management Tools
Are Important

Reduce time and make the job easier for the
security administrator

Reduce chance of configuration errors that
might result if the same changes were made
manually for each firewall on the network

Security Concerns with Remote
Management Tools

Can use a Security Information Management
(SIM) device to prevent unauthorized users from
circumventing security systems

Offers strong security controls (eg, multi
authentication and encryption)

Should have an auditing feature

Should use tunneling to connect to the firewall or use
certificates for authentication

Evaluate SIM software to ensure it does not
introduce new vulnerabilities

Basic Features Required of
Remote Management Tools

Ability to monitor and configure firewalls
from a single centralized location

View and change firewall status

View firewall’s current activity

View any firewall event or alert messages

Ability to start and stop firewalls as needed

Tracking Contents of Log Files
for Security

Reviewing log files can help detect break
ins that have occurred and possibly help
track down intruders

Tips for managing log files

Prepare usage reports

Watch for suspicious events

Automate security checks

Preparing Usage Reports

Sort logs by time of day and per hour

Check logs to learn when peak traffic times
are on the network

Identify services that consume the largest
part of available bandwidth

Preparing Usage Reports

Suspicious Events to Watch For

Rejected connection attempts

Denied connections

Error messages

Dropped packets

Successful logons to critical resources

Responding to Suspicious Events

Firewall options

Block only this connection

Block access of this source

Block access to this destination

Track the attacks

Locate and prosecute the offenders

Tools for Tracking Attacks

Sam Spade



Compiling Legal Evidence

Identify which computer or media may
contain evidence

Shut down computer and isolate work area
until computer forensic specialist arrives

Write protect removable media

Preserve evidence (make a mirror image)
so it is not manipulated


Compiling Legal Evidence

Examine the mirror image, not the original

Review log files and other data; report
findings to management

Preserve evidence by making a
“forensically sound” copy

Compiling Legal Evidence

Observe the three As of computer forensics




Automating Security Checks

Outsource firewall management

Security Breaches Will Happen!

Use software designed to detect attacks and
send alert notifications

Take countermeasures to minimize damage

Take steps to prevent future attacks

Using an Intrusion Detection
System (IDS)

Detects whether network or server has
experienced an unauthorized access attempt

Sends notification to appropriate network

Considerations when choosing


Intrusion events to be gathered

based versus host
based IDS

based versus heuristic IDS

Based IDS

Tracks traffic patterns on entire network segment

Collects raw network packets; looks at packet
headers; determines presence of known signatures
that match common intrusion attempts; takes
action based on contents

Good choice if network has been subject to
malicious activity (eg, port scanning)

Usually OS

Minimal impact on network performance

Based IDS

Collects data from individual computer on which
it resides

Reviews audit and system logs, looking for

Can perform intrusion detection in a network
where traffic is usually encrypted

Needs no additional hardware

Cannot detect port scans or other intrusion
attempts that target entire network

Based IDS

Stores signature information in a database

Database requires periodic updating

Can work with either host
based or
based IDS

Often closely tied to specific hardware and
operating system

Provides fewer false alarms than heuristic

Heuristic IDS

Compares traffic patterns against “normal
activity” and sets off an alarm if pattern

Can identify any possible attack

Generates high rate of false alarms

Receiving Security Alerts

A good IDS system:

Notifies appropriate individuals (eg, via e
alert, pager, or log)

Provides information about the type of event

Provides information about where in the
network the intrusion attempt took place

When an Intrusion Occurs

React rationally; don’t panic

Use alerts to begin assessment

Analyze what resources were hit and what damage

Perform real
time analysis of network traffic to detect
unusual patterns

Check to see if any ports that are normally unused have
been accessed

Use a network auditing tool (eg, Tripwire)

During and After Intrusion

Document the existence of:

Executables that were added to the system

Files that were

Placed on the computer


Accessed by unauthorized users

Web pages that were defaced

mail messages that were sent as a result of the attack

Document your response to the intrusion

Configuring Advanced Firewall

Ultimate goal

High availability


Advanced firewall functions

Data caching


Load balancing

Content filtering

Data Caching

Set up a server that will

Receive requests for URLs

Filter those requests against different criteria


No caching

URI Filtering Protocol (UFP) server

VPN & Firewall (one request)

VPN & Firewall (two requests)

Hot Standby Redundancy

Secondary or failover firewall is configured
to take over traffic duties in case primary
firewall fails

Usually involves two firewalls; only one
operates at any given time

The two firewalls are connected in a
heartbeat network

Hot Standby Redundancy

Hot Standby Redundancy


Ease and economy of set up and quick back
system it provides for the network

One firewall can be stopped for maintenance
without stopping network traffic


Does not improve network performance

VPN connections may or may not be included
in the failover system

Load Balancing

Practice of balancing the load placed on the
firewall so that it is handled by two or more
firewall systems

Load sharing

Practice of configuring two or more firewalls to share
the total traffic load

Traffic between firewalls is distributed by routers
using special routing protocols

Open Shortest Path First (OSPF)

Border Gateway Protocol (BGP)

Load Balancing

Load Sharing


Improves total network performance

Maintenance can be performed on one firewall
without disrupting total network traffic


Load usually distributed unevenly (can be
remedied by using layer four switches)

Configuration can be complex to administer

Filtering Content

Firewalls don’t scan for viruses but can
work with third
party applications to scan
for viruses or other functions

Open Platform for Security (OPSEC) model

Content Vectoring Protocol (CVP)

Filtering Content

Filtering Content Guidelines

Install anti
virus software on SMTP gateway in
addition to providing desktop anti
virus protection
for each computer

Choose an anti
virus gateway product that:

Provides for content filtering

Can be updated regularly to account for recent viruses

Can scan the system in real time

Has detailed logging capabilities

Chapter Summary

How to expand a firewall to meet new needs

Importance of observing fundamental principles of
network security when maintaining the firewall

Importance of being able to manage the firewall
remotely and having log files for review

Responding to security incidents

Advanced firewall functions