IDS Intrusion Detection Systems

IDS Intrusion Detection SystemsCERT definition:

A combination of hardware and software that monitors and collects system and network information and analyzes it to determine if an attack or an intrusion has occurred. Some ID Systems can automatically respond to an intrusion.

Two Models Two Models

Anomaly Detection Modeldatabase of normal activitysearch for deviations

Misuse Detection Modeldatabase of malicious signaturessearch for matches

IDS - What Can It Do?IDS - What Can It Do? Monitor and analyze user/system/network activities

Audit configuration vulnerabilities

Assess integrity of critical files

Recognize patterns of known attacks

Statistically analyze for abnormal activities

Respond with warnings and/or actions

Install decoy servers (honey pots)

Install vendor patches (some IDS)

false positive false negative

Two Types of IDSTwo Types of IDS

Network-based Intrusion Detection System (NIDS)Network-based Intrusion Detection System (NIDS)

Host-based Intrusion Detection System (HIDS)Host-based Intrusion Detection System (HIDS)

• Searches for patterns in packets, patterns of packets and packets that don’t belong.

• Can log results or communicate via SMTP/SNMP

• Sensors, analyzers and management consoles

• Searches for patterns in logs, processes, and/or memory.

• Can check file integrity (MD5)

• Observe network traffic flow

• HID also called agent

• Reactive sensors might alter router/firewall rules

• More extreme response: throttling, session hijacking

Rule-based AppliancesRule-based AppliancesSnort RulesSnort Rules

alert tcp !138.49.38.0/24 any -> 138.49.38.0/24 111\ ( content ... msg ...)

log udp any any -> 138.49.38.0/24 1:1024

alert tcp any any -> 138.49.38.0/24 ( flags:SF; msg:”possible SYN FIN scan”)

pass icmp any any <> 138.49.38.0/24 (itype:0)

IDS Disadvantages

Network-based Intrusion Detection System (NIDS)Network-based Intrusion Detection System (NIDS)

Host-based Intrusion Detection System (HIDS)Host-based Intrusion Detection System (HIDS)

• Large bandwidth can overwhelm sensor

• Sensor can view network flow, but not its impact upon host(s)

• Encryption

• Cannot see all network traffic

• Processor time

• Log file requirements

• OS vulnerabilities may impact agent

An IDS is another tool in the arsenal.

• Agents are OS specific

Example: Port Scans

IP addresses

Ports

Port sweepPort scan

Products SnortSnortSnortSnort

//www.snort.org

SourcefireSourcefireSourcefireSourcefire //www.sourcefire.com

Cisco Secure IDSCisco Secure IDSCisco Secure IDSCisco Secure IDS//www.cisco.com/go/ids/

TripwireTripwireTripwireTripwire//www.tripwire.com