FIREWALLS & NETWORK SECURITY with Intrusion Detection and VPNs, 2 nd ed. 13 Intrusion Detection and Prevention Systems By Whitman, Mattord, & Austin© 2008

FIREWALLS & NETWORK SECURITY with Intrusion Detection and VPNs, 2nd ed.

13Intrusion Detection and

Prevention Systems

By Whitman, Mattord, & Austin © 2008 Course Technology

Learning Objectives

Describe the various technologies that are used to implement intrusion detection and prevention

Define honey pots, honey nets, and padded cell systems

Describe the technologies used to create honey pots, honey nets, and padded cell systems

Slide 2Firewalls & Network Security, 2nd ed. - Chapter 13

Intrusion Detection and Prevention

Intrusion occurs when attacker attempts to gain entry or disrupt normal operations of information systems, almost always with intent to do harm

Intrusion detection consists of procedures and systems that identify system intrusions

Intrusion reaction encompasses actions an organization takes when intrusion is detected

Intrusion prevention consists of activities that deter intrusion


Intrusion Detection and Prevention (continued)

Intrusion correction activities finalize restoration of operations to a normal state and seek to identify source and method of intrusion to ensure same type of attack cannot occur again

Intrusion detection systems (IDSs) work like a burglar alarm: detect violation, activate alarm

Intrusion prevention system (IPS) can detect intrusion and launch an active response

IDS and IPS systems often coexist Intrusion detection/prevention system (IDPS)

describes current anti-intrusion technologies Slide 4Firewalls & Network Security, 2nd ed. - Chapter 13

IDPS Terminology

Alert or alarm: indication a system has just been attacked or is under attack

Evasion: process by which attacker changes the format and/or timing of their activities to avoid being detected by the IDPS

False attack stimulus: event that triggers alarm when no actual attack is in progress

False negative: failure of an IDPS to react to an actual attack event

False positive: alert or alarm that occurs in the absence of an actual attack


IDPS Terminology (continued)

Noise: accurate alarm events that do not pose significant threat to information security

Site policy: rules and configuration guidelines governing implementation and operation of IDPSs within an organization

Site policy awareness: IDPS’s ability to dynamically modify its configuration in response to environmental activity

True attack stimulus: event that triggers alarms and causes an IDPS to react as if a real attack is in progress


IDPS Terminology (continued)

Tuning: process of adjusting IDPS to maximize efficiency in detecting true positives, while minimizing false positives and false negatives

Confidence value: value placed upon an IDPS’s ability to detect/identify certain attacks correctly

Alarm filtering: running system for a while to track types of false positives it generates and then adjusting IDPS alarm classifications

Alarm clustering and compaction: process of grouping almost identical alarms occurring at almost same time into single higher-level alarm


Why Use an IDPS?

NIST reasons to acquire and use an IDPS:– To prevent problem behaviors by increasing the

perceived risk of discovery and punishment

– To detect attacks and other security violations not prevented by other security measures

– To detect and deal with the preambles to attacks

– To document existing threat to an organization

– To act as quality control for security design and administration

– To provide useful information about intrusions that do take place


Why Use an IDPS? (continued)

IPS technologies can respond to detected threat by attempting to prevent it from succeeding while IDS cannot

IDPS operational categories:– Host-based (operates on the hosts themselves)

– Network-based (functions at the network level)• Wireless• Network behavior analysis (NBA)


Why Use an IDPS? (continued)

Several IPS response techniques:– Terminate network connection or user session

that is being used for the attack

– Block access to target from offending user account, IP address, or other attacker attribute

– Block all access to targeted host, service, application, or other resource

– Change the security environment

– Change the attack’s content


Network-Based IDPS

NIDPSs reside on computer or appliance connected to network segment and monitor network traffic

Compare measured activity to known signatures to determine whether an attack has occurred or is underway

Protocol stack verification: NIDPSs look for invalid data packets

Application protocol verification: higher-order protocols (HTTP, FTP, Telnet) are examined for unexpected packet behavior or improper use


Network-Based IDPS (continued)

Some advantages of NIDPSs:– Good network design and placement of devices

can enable organization to use a few devices to monitor large network

– Usually passive devices and can be deployed into existing networks with little or no disruption to normal network operations

– Not usually susceptible to direct attack and may not be detectable by attackers


Network-Based IDPS (continued)

Some disadvantages of NIDPSs:– Can become overwhelmed by network volume

and fail to recognize attacks they might otherwise have detected

– Require access to all traffic to be monitored– Cannot analyze encrypted packets, making some

of the network traffic invisible to the process– Cannot reliably ascertain if an attack was

successful or not– Some forms of attack are not easily discerned,

specifically those involving fragmented packets


Wireless NIDPS

Monitors and analyzes wireless network traffic looking for potential problems with wireless protocols (Layers 2 and 3 of the OSI model)

Cannot evaluate and diagnose issues with higher-layer protocols like TCP and UDP

Some issues with implementation include:– Physical security– Sensor range– Access point and wireless switch locations– Wired network connections– Cost


Network Behavior Analysis System

Examines network traffic to identify problems related to flow of traffic

Uses a version of anomaly detection method Typical flow data relevant to intrusion detection

and prevention includes:– Source and destination IP addresses– Source and destination TCP or UDP ports or ICMP

types and codes– Number of packets and bytes transmitted in the

session– Starting and ending timestamps for the session


Network Behavior Analysis System (continued) Typically monitors internal networks; occasionally

monitors internal/external network connections Most sensors, passive mode deployment only Types of events most commonly detected by

NBA sensors include:– Denial-of-service (DoS) attacks (including DDoS)– Scanning– Worms– Unexpected application services– Policy violations


Host-Based IDPS

Resides on particular computer or server (the host) and monitors activity only on that system

Also known as system integrity verifiers Benchmark/monitor status of key system files Triggers alert when file attributes change, new

files are created, or existing files are deleted Managed HIDPSs can monitor multiple computers

simultaneously by creating a configuration file on each monitored host and by making each HIDPS report back to a master console system


Host-Based IDPS (continued)

Some advantages of HIDPSs:– Can detect local events on host systems and also

detect attacks that may elude NIDPSs– Functions on host system, where encrypted traffic

will have been decrypted and is available for processing

– Unaffected by use of switched network protocols– Can detect inconsistencies in how applications and

systems programs were used by examining records stored in audit logs, enabling it to detect some types of attacks, including Trojan Horse programs


Host-Based IDPS (continued)

Some disadvantages of HIDPSs:– Pose more management issues since they are

configured/managed on each monitored host

– Vulnerable to direct attacks, attacks on host OS

– Not optimized to detect multi-host scanning; unable to detect scanning of non-host devices

– Susceptible to some denial-of-service attacks

– Can use large amounts of disk space to retain the host OS audit logs

– Inflicted overhead on host systems may reduce system performance below acceptable levels


IDPS Detection Methods

Signature-based (knowledge-based, misuse-detection) IDPS: examines network traffic in search of patterns that match known signatures

Statistical anomaly-based (stat, behavior-based) IDPS: compares sampled network activity to established baseline

Stateful protocol analysis (SPA) IDPS: uses profiles to detect anomalous protocol behavior

Log file monitor (LFM) IDPS: reviews log files from servers, network devices, and other IDPSs for signatures indicating an attack or intrusion


IDPS Response Behavior

Response depends on organization’s policy, objectives, and system capabilities

Responses classified as active or passive Active response: definitive action automatically

initiated when certain types of alerts are triggered; can include collecting additional data, changing or modifying the environment, and taking action against the intruders

Passive response: report information they have collected and wait for administrator to act


IDPS Response Behavior (continued)

Some possible responses IDPSs can produce:– Audible/visual alarm

– SNMP traps and plug-ins

– E-mail message

– Page or phone message

– Log entry

– Evidentiary packet dump

– Take action against the intruder

– Launch program

– Reconfigure firewall

– Terminate session or connection


Selecting IDPS Approaches and Products

Technical and policy considerations– What is your system’s environment?

– What are your security goals and objectives?

– What is your existing security policy? Organizational requirements and constraints

– What requirements are levied from outside the organization?

– What are your organization’s resource constraints?


Selecting IDPS Approaches and Products (continued)

IDPSs product features and quality– Is the product sufficiently scalable for your

environment?

– How has the product been tested?

– What is the user level of expertise targeted by the product?

– Is the product designed to evolve as the organization grows?

– What are the support provisions for the product?


Strengths and Limitations of IDPSs

IDPSs perform the following functions well:– Monitoring and analysis of system events and

user behaviors

– Testing security states of system configurations

– Baselining security state of system and then tracking any changes to that baseline

– Recognizing patterns of system events that correspond to known attacks

– Recognizing patterns of activity that statistically vary from normal activity


Strengths and Limitations of IDPSs (continued)

More functions that IDPSs perform well:– Managing operating system audit and logging

mechanisms and the data they generate

– Alerting appropriate staff by appropriate means when attacks are detected

– Measuring enforcement of security policies encoded in the analysis engine

– Providing default information security policies

– Allowing non-security experts to perform important security monitoring functions


Strengths and Limitations of IDPSs (continued)

IDPSs cannot perform the following functions:– Compensating for weak or missing security

mechanisms in the protection infrastructure– Instantaneously detecting, reporting, responding to

attack during heavy network/processing load– Detecting newly published attacks or variants– Effectively responding to sophisticated attacks– Automatically investigating attacks– Resisting all attacks intended to defeat them– Compensating for fidelity issues of data sources– Dealing effectively with switched networks


Deployment and Implementation of an IDPS

IDPS control strategies– Centralized: all IDPS control functions are

implemented and managed in a central location

– Fully distributed: all control functions are applied at the physical location of each IDPS component

– Partially distributed: combines the best of the other two strategies; while individual agents still analyze and respond to local threats, their reporting to a hierarchical central facility enables the organization to detect widespread attacks


Deployment and Implementation of an IDPS (continued)

IDPS deployment– Great care must be made in deciding where to

locate IDPS components, physically and logically

– During deployment, each component should be installed, configured, fine-tuned, tested, and monitored

– NIDPS and HIDPS used in tandem can protect individual systems and organizational networks

– Use a phased implementation strategy so as not to affect entire organization all at once

– First implement NIDPSs and then install HIDPSs



Deploying network-based IDPSs– NIST recommends four locations for NIDPS

sensors:• Behind each external firewall, in the network DMZ• Outside an external firewall• On major network backbones• On critical subnets



Deploying host-based IDPSs– Proper implementation of HIDPSs can be a

painstaking and time-consuming task, as each HIDPS must be custom configured to its host

– May be beneficial to practice an implementation on one or more test servers beforehand

– Installation continues until either all systems are installed or organization reaches the planned degree of coverage it is willing to live with


Measuring the Effectiveness of IDPSs

When selecting an IDPS, one typically looks at four measures of comparative effectiveness:– Thresholds

– Blacklists and whitelists

– Alert settings

– Code viewing and editing


Measuring the Effectiveness of IDPSs (continued)

Once implemented, IDPSs are evaluated using two dominant metrics: – Administrators evaluate the number of attacks

detected in a known collection of probes

– Administrators examine the level of use, commonly measured in megabits per second of network traffic, at which the IDPSs fail

In order to truly assess effectiveness of IDPS systems, test process should be as realistic as possible in its simulation of actual event

Couple realistic traffic loads, levels of attacks Slide 33Firewalls & Network Security, 2nd ed. - Chapter 13

Honey Pots, Honey Nets, and Padded Cell Systems

Honey pots (decoys, lures, fly-traps): decoy systems designed to lure potential attackers away from critical systems

Honey net: collection of honey pots connecting several honey pot systems on a subnet

Honey pots are designed to:– Divert an attacker from critical systems

– Collect information about the attacker’s activity

– Encourage the attacker to stay on the system long enough for administrators to document the event and, perhaps, respond


Honey Pots, Honey Nets, and Padded Cell Systems (continued)

Padded cell: honey pot that has been protected so it cannot be easily compromised—in other words, a hardened honey pot

In addition to attracting attackers with tempting data, padded cell operates in tandem with traditional IDPS

When IDPS detects attackers, it seamlessly transfers them to special simulated environment where they can cause no harm

Allows organization to observe and document actions and tactics of an attacker



Advantages of using honey pot or padded cell:– Attackers can be diverted to targets that they

cannot damage

– Administrators have time to decide how to respond to an attacker

– Attackers’ actions can be easily and more extensively monitored, and the records can be used to refine threat models and improve system protections

– Honey pots may be effective at catching insiders who are snooping around a network



Disadvantages of using honey pot or padded cell:– The legal implications of using such devices are

not well defined

– Honey pots and padded cells have not yet been proven as generally useful security technologies

– An expert attacker, once diverted into a decoy system, may become angry and launch a more hostile attack against an organization’s systems

– Administrators and security managers need a high level of expertise to use these systems


Trap and Trace Systems

Use a combination of techniques to detect an intrusion and then to trace it back to its source

Trap usually consists of a honey pot or padded cell and an alarm

Trace feature is process by which organization attempts to determine identity of an intruder


Trap and Trace Systems (continued)

If intruder is someone inside the organization, administrators are within their power to track the individual and turn him or her over to authorities

If intruder is outside security perimeter of the organization, numerous legal issues arise

Back hack: hacking into a hacker’s system to find out as much as possible about the hacker

Enticement or entrapment?


Active Intrusion Prevention

Some organizations do more than wait for an attack and implement active countermeasures

When attacker sends ARP request to unused IP address, LaBrea pretends to be a computer at that address, allowing attacker to connect

Once connected, LaBrea changes TCP sliding window size to a low number to hold open the connection from the attacker

This greatly slows down network-based worms and other attacks and gives LaBrea system time to notify system and network administrators


Chapter Summary

Intrusion occurs when attacker attempts to gain entry or disrupt normal operations of information system, almost always with intent to do harm

Intrusion detection consists of procedures and systems that identify system intrusions

Intrusion reaction encompasses actions an organization takes when intrusion is detected

Intrusion prevention consists of activities that deter an intrusion


Chapter Summary (continued)

Intrusion detection system (IDS) works like a burglar alarm: detects violation, activates alarm

Intrusion prevention system (IPS) can prevent intrusion from successfully attacking the organization by means of some active response

Because these systems often coexist, term intrusion detection/prevention system (IDPS) is used to describe current anti-intrusion technologies



IDPSs commonly operate as either network- or host-based systems

Network-based IDPS functions at network level Host-based IDPS operates on hosts themselves Systems that use both approaches are called

hybrid IDPSs



IDPSs use variety of detection methods to monitor and evaluate network traffic

Three methods dominate: signature-based approach, statistical-anomaly approach, stateful protocol analysis approach

Log file monitor (LFM) IDPS is similar to NIDPS Using LFM, system reviews log files generated by

servers, network devices, and other IDPSs, looking for patterns and signatures that may indicate an attack or intrusion is in progress or has already occurred



Honey pots: decoy systems designed to lure potential attackers away from critical systems

Honey net: collection of honey pots connecting several honey pot systems on a subnet

A honey pot is configured in ways that make it look vulnerable to lure potential attackers into attacking, thereby revealing themselves

Trap and trace applications use a combination of techniques to detect intrusion and then trace it back to its source


Documents

FIREWALLS & NETWORK SECURITY with Intrusion Detection and VPNs, 2 nd ed. 13 Intrusion Detection and Prevention Systems By Whitman, Mattord, & Austin© 2008