📝 This post is a summarized version of Beginner’s Guide to IDS vs IPS in Cyber Security by Aleksa Tamburkovski, originally published on the ZTM blog.
For the full post and more in-depth insights, check out the original article.
You’ve probably seen IDS and IPS mentioned in job listings or security docs. But what do they actually do, and how are they different?
This guide breaks down both tools in simple terms — no fluff, no jargon — so you can actually understand what’s happening when your network is under threat.
🚨 What is an Intrusion Prevention System (IPS)?
An IPS is an active gatekeeper. It doesn’t just detect threats — it blocks them in real time.
For example: If someone is brute-forcing your login form, an IPS can detect the pattern and block them instantly.
Where it sits: Directly in-line with traffic. Every request goes through it.
How it works:
- Signature-based: Matches known attack patterns
- Anomaly-based: Flags weird behavior
- Policy-based: Custom rules you define
Gotchas:
Because it can block traffic, an IPS has to be finely tuned. Misconfigurations could lead to service disruptions — which is why teams often run it in passive mode first, to see what it would block.
Popular tools: Cisco Firepower, Palo Alto Threat Prevention, Suricata, Snort
👀 What is an Intrusion Detection System (IDS)?
An IDS is more like a security camera. It watches traffic and alerts you if something looks suspicious — but it doesn’t block it.
This makes IDS ideal for spotting:
- Lateral movement inside your network
- Strange login behavior
- New, unknown attacks that don’t match a signature
Where it sits: Out-of-band, watching a copy of traffic. It won’t slow things down or interfere.
How it detects threats:
- Signature-based: Fast and accurate for known threats
- Anomaly-based: Useful for zero-days, but needs tuning
Popular IDS tools: Snort, Zeek, Suricata (in IDS mode)
🧠 IDS vs IPS: Key Differences
| Feature | IDS | IPS |
|---|---|---|
| Response | Passive (alerts) | Active (blocks threats) |
| Placement | Out-of-band | In-line with traffic |
| Risk | Low (no interference) | Medium-High (if misconfigured) |
| Detection Methods | Signature + Anomaly | Signature + Anomaly + Policy |
| Best Use | Internal monitoring | Real-time protection |
⚠️ Common Mistakes to Avoid
- Turning them on without tuning — Always start in monitoring mode.
- Relying on default rules — Customize for your environment.
- Using only signatures — Combine with anomaly detection.
- Not integrating with workflows — Make sure alerts go somewhere actionable (like your SIEM).
🛡️ Why You Need Both
It’s not IDS vs IPS — it’s IDS + IPS.
- Use IPS for real-time protection (e.g. login portals, APIs)
- Use IDS for internal visibility and threat context
Tools like Snort and Suricata support both modes. Start with IDS mode, tune it, then switch to IPS when ready.
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Check out the Advanced Ethical Hacking Bootcamp: Network Hacking & Security
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🔐 This post is a condensed summary. For the full guide, examples, and deeper context, read the original: Beginner’s Guide to IDS vs IPS in Cyber Security by Aleksa Tamburkovski on the ZTM blog.
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