Full Definition
What is an Intrusion Detection System?
An Intrusion Detection System (IDS) is a device or software application that monitors a network or systems for malicious activity or policy violations. It analyzes traffic and generates alerts when suspicious activity is detected.
IDS Types
Network IDS (NIDS)
- Monitors network traffic
- Analyzes packets
- Placed at network boundaries
Host IDS (HIDS)
- Monitors individual hosts
- File integrity monitoring
- System call analysis
Hybrid IDS
- Combines NIDS and HIDS
- Comprehensive coverage
- Correlation across sources
Detection Methods
Signature-Based
- Known attack patterns
- High accuracy for known threats
- Requires constant updates
Anomaly-Based
- Baseline behavior
- Detects unknown threats
- Higher false positives
Behavior-Based
- User/entity behavior
- Machine learning
- Adaptive detection
IDS vs. IPS
| IDS | IPS |
|---|---|
| Detects threats | Prevents threats |
| Passive monitoring | Active blocking |
| Alerts only | Takes action |
| No network delay | Inline processing |
Common IDS Solutions
Open Source
- Snort
- Suricata
- Zeek (Bro)
- OSSEC
Commercial
- Cisco Firepower
- Palo Alto
- Trend Micro
Deployment Considerations
- Network architecture
- Traffic volume
- Tuning and maintenance
- Alert management
- Integration with SIEM