Security Technology: Intrusion Detection, Access Control and Other Security Tools

Chapter 7

Intrusion

“Intrusion is a type of attack on information assets in which the instigator attempts to gain entry into a system or disrupt the normal operation of system with, almost always, the intent to do malicious harm.”

Definitions

Intrusion prevention: activities that deter an intrusion Writing &implementing a good enterprise information security

policy Planning & executing effective information security programs Installing & testing technology-based countermeasures Conducting & measuring the effectiveness

Employee training and awareness activities Intrusion detection: procedures and systems that identify sys

intrusions Intrusion correction:

Activities finalize the restoration of operations to a normal state Activities seek to identify the source & method of attack for

prevention

Intrusion Detection Systems Commercially available in late 1990 Works like a burglar alarm Detects a violation and sounds alarm Extension – Intrusion prevention systems

Detect and prevent intrusion Generally accepted combination

Intrusion detection and prevention system (IDPS)

IDPS Terminology

Alarm or alert: indication that attack is happening Evasion: attacker change the format and/or timing of

activities to avoid being detected False attack stimulus: event triggers alarm – no real

attack False negative: failure of IDPS to react to attack False positive: alarm activates in the absence of an actual

attack Noise: alarms events that are accurate but do not pose

threats Site policy: rules & configuration guidelines governing the

implementation & operation of IDPS

IDPS Terminology

Site policy awareness: ability to dynamically modify config in response to environmental activity

True attack stimulus: event that triggers alarms in event of real attack

Tuning: adjusting an IDPS Confidence value: measure IDPS ability correctly

detect & identify type of attacks Alarm filtering: Classification of IDPS alerts Alarm clustering and compaction: grouping almost

identical alarms happening at close to the same time

Why Use an IDS

Prevent problem behaviors by increasing the perceived risk of discovery and punishment

Detect attacks and other security violations Detect and deal with preambles to attacks Document existing threat to an

organization Act as quality control for security design &

administration Provide useful information about intrusions

that take place

Types of IDS Network based

Focused on protection network information assets Wireless Network behavior analysis

Host-based Focused on protection server of host’s information assets

Network-Based Resides on computer or appliance connected

to an a segment of orgs. network Monitors network traffic on the segment Monitors packets Monitoring port (switched port analysis)

Monitors all ingoing and outgoing traffic Looks for attack patterns Compares measured activity to known

signatures Protocol verification – packet structure Application verification – packet use

Advantages and DisadvantagesAdvantages

Needs few devices to monitor large network Little or no disruption to normal operations May not be detectable by attackers

Disadvantages Overwhelmed by network volume Requires access to all traffic Cannot analyze encrypted packets Cannot ascertain if an attack was successful Some forms of attack are not easily discerned

Fragmented packetsMalformed packets

Wireless NIDPS

Monitors and analyzes wireless network traffic Looks for potential problems with the wireless protocols

(layers 2 and 3) Cannot evaluate & diagnose issue with higher level

layers Issues associated with implementation

Physical security Sensor range Access point and wireless switch locations Wired network connections Cost

Wireless NIDPS

Can detect conditions in addition to traditional types of IDSPS Unauthorized WLAN and WLAN devices Poorly secured WLAN devices Unusual usage patterns The use of wireless network scanners DoS attacks and condition Man-in-middle attacks

Unable to detect Passive wireless protocol attacks Susceptible to evasion techniques Susceptible to logical and physical attacks on wireless access

point

Host-Based Resides on a particular computer or server & monitors

traffic only on that system Also known as system integrity verifiers Works on principle of configuration and change

management Classifies files in categories & applies various

notification actions based on rules Maintains own log file Can monitor multiple computers simultaneously

Advantages Reliable Can detect local events Operates on host system where encrypted files already

decrypted and available Use of switched network protocols does not affect Can detect inconsistencies in how application and system

programs were used

Disadvantages

Pose more management issues Configured and maintained on each host

Vulnerable both to direct attacks and attacks against the host operating system

Not optimized to detect multi-host scanning

Disadvantages

Not able to detect scanning of non-host devices (routers and switches)

Susceptible to Denial of Service attacksCan use large amounts of disk space – audit

logsCan inflict a performance overhead on host

systems

Application Based

Examines application for abnormal events Looks for files created by application Anomalous occurrences – user exceeding authorization

Tracks interaction between users and applications

Able to tract specific activity back to individual user

Able to view encrypted data Can examine encryption/decryption

process

Advantages & Disadvantages Advantages

Aware of specific users Able to operate on encrypted data

Disadvantages More susceptible to attack Less capable of detecting software tampering

IDS Methodologies

Types determined by where placed for monitoring purposes

IDS methodologies based on detection methods Two dominate methodologies

Signature-based (knowledge-based) Statistical-anomaly approach

Signature Based

Examines data traffic in search of patterns that match known signature Foot printing and fingerprinting activities Specific attack sequences DOS

Widely used Signature database must be continually updated Attack time-frame sometimes problematic

Slow and methodical may slip through

Statistical Anomaly Based

Based on frequency on which network activities take place

Collect statistical summaries of “normal” traffic to form baseline

Measure current traffic against baseline Traffic outside baseline will generate alert Can detect new type of attacks Requires much more overhead and processing

capacity May not detect minor changes to baseline

Log file Monitors

Similar to NIDS Reviews logs Looks for patterns & signatures in log files Able to look at multiple log files from different

systems Large storage requirement

Responses to IDS

Vary according to organization policy, objectives, and system capabilities

Administrator must be careful not to increase the problem

Responses active or passive

Which One?

Consider system environment Technical specification of systems environment Technical specification of current security protections Goals of enterprise Formality of system environment and management culture

Which One?

Consider Security Goals and Objectives Protecting from threats out organization? Protecting against inside? Use output of IDS to determine new hardware/software

needs Maintain managerial over one-security related network

usage

Which One?

Security policy Structure Job descriptions of system user Include reasonable use policy What are you going to do if violation occurs

Which One?

Organization Requirements and Constraints? Outside Requirements Resource Constraints

Features and Quality Tested Product User Level of Expertise Product Support

Strengths of IDS

Monitoring & analysis of system events & user behaviors Testing security states of system configuration Base lining security state of the system & track changes

to baseline Pattern recognition Auditing and logging Alerting Measuring performance

Limitations of IDS

Compensate for weak or missing security mechanisms Instantly report or detect during heavy operations Detect newly published attacks Effectively respond to sophisticated attackers Automatic investigate Keep attacks from circumventing them Deal effectively with switched networks

Control Strategies

Centralized Partially distributed Fully distributed

Centralized

All IDS control functions are implemented and managed in a centralized location

1 management system Advantages

Cost and control Specialization

Disadvantage

Fully Distributed

Opposite of centralized All control functions applied at the physical location

of each IDS component Each sensor/agent is best configured to deal with its

own environment Reaction to attacks sped up

Partially Distributed Control

Individual agents respond to local threats Report to a hierarchical central facility One of the more effective methods

Honey Pots / Honey Nets / Padded Cell Systems

Honey Pots Decoy systems Lure potential attackers away from critical systems Encourages attacks against themselves

Honey Net Collection of honey pots Connects honey pots on a subnet Contains pseudo-services the emulated well-known services Filled with factious information

Honey Pots / Honey Nets / Padded Cell Systems

Padded Cell Protected honey pot IDS detects attacks and transfers to simulated environment Monitors action of attacker

Trap and Trace Systems

Detect intrusion and trace incident back Consist of honey pot or padded cell & alarm Similar to concept of caller ID Back-hack

Considered unethical Legal drawbacks to trap and trace

Enticement and entrapment

Scanning and Analysis Tools Help find vulnerabilities in system, holes in security

components, and unsecure aspects of the network Allow system admin to see what the attacker sees May run into problems with ISP Port scanners – what is active on computer Firewall analysis tools Operating system detection tools Vulnerability scanners Packet sniffers

Access Control Tools

Authentication – validation of users identity 4 general ways carried out

What he knows What he has Who he is What he produces