An Intrusion Detection System watches your network or hosts for signs of an attack and tells you about it — it does not, on its own, stop anything. That distinction gets lost constantly in “best IDS software” roundups that quietly recommend an IPS or a full SIEM instead, and it matters: buying the wrong category of tool leaves you either under-protected or paying for correlation and retention you don’t need yet.
This page compares the six tools actually deployed by security teams in 2026 — five open-source, one commercial — on what they detect, how they deploy, and what they genuinely cost once you count the engineering time the “free” ones aren’t free of.
Executive Answer
- Most widely documented, easiest to hire for: Snort. Cisco-backed, GPLv2+, the largest body of community rules and troubleshooting precedent of any tool here.
- Best raw performance on high-throughput networks: Suricata. Multi-threaded by design, where Snort’s older architecture is single-threaded per instance.
- Deepest visibility, if you’re willing to script: Zeek. Behavioral and protocol analysis rather than signature matching — a different tool for a different question.
- Watching hosts, not the network: Wazuh. Log and file-integrity monitoring, and the one open-source option here with a real managed-cloud product if you don’t want to run the infrastructure yourself.
- Want it pre-integrated instead of assembled: Security Onion. Bundles Suricata, Zeek, and Wazuh into one deployable distribution.
- Want a vendor to call when it breaks: SolarWinds Security Event Manager, the one commercial, quote-priced option on this page.
What IDS Software Actually Does — and What It Doesn’t
An IDS monitors traffic or system logs and flags suspicious patterns. It does not block traffic — that’s the job of an Intrusion Prevention System (IPS). In practice this distinction has blurred: most modern engines, Suricata and Snort included, can run in either mode depending on configuration, so “IDS vs IPS” is now largely a deployment choice rather than a product choice. What hasn’t blurred is the purpose — an IDS is fundamentally a visibility tool, telling you what happened, and treating it as an active defense is a mistake that shows up during an actual incident, not during setup.
You need one if you run infrastructure that’s a plausible target — anything handling customer data, payment information, or internal systems reachable from the internet. A small site with no sensitive data behind it often gets more immediate value from solid firewall logging and a web application firewall before an IDS deployment is the right next investment.
The Six Tools, Compared
| Tool | Type | Detection method | License | Best for |
|---|---|---|---|---|
| Snort | Network (NIDS/NIPS) | Signature-based | Free, open-source (Cisco) | Widest documentation and community rules |
| Suricata | Network (NIDS/NIPS) | Signature + anomaly | Free, open-source | Multi-threaded, higher-throughput networks |
| Zeek | Network (NIDS) | Behavioral/protocol analysis | Free, open-source | Deep traffic analysis, custom scripting |
| Wazuh | Host (HIDS) + SIEM-adjacent | Log & file-integrity | Free open-source; Cloud from $571/mo | Endpoint monitoring, managed option available |
| Security Onion | Network + host | Bundles Suricata, Zeek, Wazuh | Free, open-source distro | Pre-integrated stack instead of DIY assembly |
| SolarWinds SEM | Network + host (SIEM-adjacent) | Signature + correlation | Commercial, quote-priced | Vendor support over a DIY open-source stack |
Which of these six tools actually fits your setup?
Answer four questions. Each answer’s point weights are visible in the page source next to the option — nothing hidden in the scoring.
The Tools, In Detail
Snort — the default for a reason
Snort is Cisco’s open-source network intrusion detection and prevention engine, currently on the Snort 3 branch (v3.12.2.0 as of April 2026), licensed GPLv2+. Talos, Cisco’s threat intelligence group, publishes rule updates roughly twice weekly, with out-of-cycle releases for critical vulnerabilities.
The reason Snort is the default recommendation isn’t that it’s technically superior to Suricata — on raw multi-threaded throughput, it generally isn’t. It’s that Snort has the largest body of community documentation, Stack Exchange precedent, and third-party tooling of any IDS on this list. When something goes wrong at 2am, there’s a meaningfully higher chance someone has already written up the exact problem you’re looking at. That’s a real, if unglamorous, reason to choose a tool.
Suricata — built for the traffic Snort’s architecture struggles with
Suricata is maintained by the Open Information Security Foundation and is free and open-source. Its core architectural difference from Snort is multi-threading — it can use multiple CPU cores for a single instance’s packet inspection, where Snort traditionally runs one thread per process. On a high-throughput network, that difference is the whole decision.
Suricata also natively combines signature-based and anomaly-based detection, and can consume many existing Snort rulesets directly, which lowers the switching cost if you’re migrating from Snort rather than starting fresh.
Zeek — not really competing with the other two
Zeek (formerly Bro) takes a fundamentally different approach: instead of matching traffic against a signature database, it builds a detailed log of network activity and lets you script custom detection logic against it in its own domain-specific language. This makes it less of an out-of-the-box alerting tool and more of a platform for security teams who want to ask specific, custom questions of their traffic.
The honest framing: Zeek is not a drop-in Snort or Suricata replacement. Teams frequently run it alongside one of the other two — Zeek for deep, custom analysis and incident investigation, Snort or Suricata for standard signature-based alerting. Security Onion, below, bundles this exact combination.
Wazuh — the one built for hosts, and the one with a managed option
Wazuh is free, open-source, and fundamentally different from the three above: it’s host-based (HIDS), watching logs and file integrity on individual servers rather than inspecting network traffic. If your actual concern is “did someone modify a file on this server” or “what do these application logs show,” Wazuh is the right category of tool, not Snort or Suricata.
Self-hosted Wazuh has no licence fee, but running it at real scale is not free — you’re paying in infrastructure and, more significantly, in the engineering time to deploy, tune detection rules, manage false positives, and maintain the indexer cluster. For teams that want the capability without building that operational expertise in-house, Wazuh Cloud (the managed version) starts at $571/month for up to 100 agents, rising to $923/month for 250 agents and $1,467/month for 500 — verified directly from Wazuh’s own pricing page. Support beyond the platform itself is sold separately, in Standard and Premium SLA tiers with response times rather than flat pricing.
Security Onion — the pre-assembled version of the DIY stack
Security Onion is a free, open-source Linux distribution that bundles Suricata, Zeek, and Wazuh (plus supporting infrastructure) into one deployable package with a unified interface. The pitch is straightforward: instead of separately standing up, configuring, and integrating three tools, you deploy one distribution that’s already done that integration work.
The trade-off is flexibility for convenience — you inherit Security Onion’s specific integration choices and update cadence rather than assembling exactly the stack you’d choose piece by piece. For a team without deep experience standing up each component individually, this is very likely the faster and more defensible path to a working deployment.
SolarWinds Security Event Manager — the commercial alternative
SolarWinds SEM is a commercial SIEM-adjacent platform combining signature-based detection with log correlation across network and host sources, aimed specifically at teams who want a vendor relationship and a managed interface rather than a self-assembled open-source stack.
We could not verify a single, reliable price for SEM. SolarWinds’ own pricing page did not return pricing details on request, and third-party sources we checked disagree substantially — figures ranging from roughly $1,789 to $4,665+ depending on node count and licensing model, with no consistent methodology behind the discrepancy. Rather than repeat a number we can’t stand behind, our advice is to request a quote directly and treat any third-party “SolarWinds SEM costs $X” claim you encounter elsewhere with real skepticism until you’ve confirmed it against SolarWinds’ own sales process.
Open-Source vs. Commercial: What Actually Matters
The open-source tools here — Snort, Suricata, Zeek, Wazuh, Security Onion — cost nothing to license. What they cost is time: someone on your team tuning rulesets, triaging false positives, and keeping the deployment patched and running. For Wazuh specifically, third-party total-cost-of-ownership estimates for a mid-market self-hosted deployment run in the $15,000–$40,000 per year range for infrastructure alone, before the cost of the engineering time to run it — we flag this as directional, not verified against a primary source, but it’s a useful sense check before assuming “free” tools are actually free at production scale.
Commercial platforms like SolarWinds SEM trade that setup and tuning burden for a subscription cost and a vendor support relationship. The calculus that actually matters: if you already have security engineers who’d be tuning detection rules regardless of which tool sits underneath, the open-source stack often wins outright. If you don’t have that staff and would otherwise be hiring for it, a commercial platform’s cost frequently compares favourably to the salary of the person you’d need to run the DIY stack well.
IDS vs. IPS vs. SIEM
- IDS — detects and alerts. Does not block traffic.
- IPS — detects and actively blocks or drops malicious traffic. Snort and Suricata can both run in this mode.
- SIEM — aggregates logs and alerts from multiple sources, including your IDS, for correlation and long-term retention. An IDS is typically one input into a SIEM, not a replacement for one. SolarWinds SEM and Wazuh both lean into this adjacent territory rather than staying pure-IDS.
How to Choose
- Network traffic or host activity? Network → Snort, Suricata, or Zeek. Hosts and logs → Wazuh.
- Do you have staff to tune an open-source stack? If yes, start there — it’s free to license and the community precedent is deep. If no, price SolarWinds SEM against the cost of hiring for that expertise.
- High-throughput network? Suricata’s multi-threading is the practical answer over Snort’s traditional single-thread-per-instance model.
- Want deep custom investigation, not just alerting? Add Zeek alongside whichever signature engine you choose — it’s not a replacement for one.
- Don’t want to assemble the stack yourself? Security Onion bundles the network-plus-host combination pre-integrated.
Frequently Asked Questions
Is a free, open-source IDS good enough for a small business?
For most small teams, yes — Suricata or Security Onion cover the majority of use cases without licensing cost. The real trade-off is your own time spent on setup and ongoing tuning, not a capability gap versus commercial tools.
Do I need both an IDS and an IPS?
Most current deployments run in combined IDS/IPS mode rather than choosing one or the other — the same engine, Suricata for example, operates as either depending on configuration. The distinction matters for understanding what you’re deploying, less so for picking two separate products.
How much traffic can these tools realistically handle?
This depends far more on your hardware and rule complexity than on the tool itself. Benchmark against your own actual traffic profile before committing to a deployment size — published throughput figures from any vendor are a starting point, not a guarantee.
Can I migrate from Snort to Suricata without starting over?
Largely, yes — Suricata is built to consume many existing Snort rule formats directly, which is one of the more common upgrade paths when a network’s throughput outgrows a single-threaded Snort deployment.
Does Wazuh replace a SIEM entirely?
For many small-to-mid deployments, close to it — Wazuh’s log aggregation and correlation cover a meaningful share of what a dedicated SIEM does. At real enterprise scale, most teams still pair it with, or eventually graduate to, a dedicated SIEM platform for retention and correlation depth Wazuh alone doesn’t target.
How We Assessed These
Every open-source tool’s licensing status and current version was verified against its own project pages or Cisco’s official documentation at the time of writing. Wazuh Cloud’s pricing is quoted directly from wazuh.com. SolarWinds SEM’s pricing could not be independently verified — we say so explicitly rather than repeating a third-party figure. Disclosure: no tool on this page is linked through an affiliate relationship.
