The Open Source Landscape
There are more open source network monitoring and DDoS-adjacent tools than ever. The challenge is that most are general-purpose network tools with some DDoS detection bolted on, not purpose-built DDoS detection platforms. Knowing the difference saves you from deploying a tool and discovering it does not solve the problem you thought it would.
Purpose-Built DDoS Tools
ftagent-lite (Flowtriq)
ftagent-lite is Flowtriq's open source standalone monitor. It reads kernel-level network counters per-second, detects traffic anomalies, and sends alerts. It is designed for operators who want basic DDoS detection without a SaaS subscription.
What it does: Per-second PPS and bandwidth monitoring, threshold-based alerting, basic attack classification, webhook notifications.
What it does not do: Dynamic baselines, PCAP capture, automated mitigation, multi-node dashboard, BGP integration. Those features are in the full ftagent with a Flowtriq subscription.
Install: pip install ftagent
NetHawk (Flowtriq)
NetHawk is a Go-based TUI (terminal user interface) traffic analyzer. It provides real-time traffic visualization in the terminal with protocol breakdown, top talkers, and bandwidth graphs.
What it does: Real-time traffic visualization, protocol analysis, top talker identification, anomaly highlighting. Useful for quick diagnostics and during-incident investigation.
What it does not do: Persistent monitoring, alerting, mitigation, multi-node management.
General-Purpose Tools with DDoS Capabilities
ntopng
ntopng is a network traffic probe and flow collector. Its Community Edition provides real-time traffic analysis, protocol breakdown, and basic anomaly alerting. The Enterprise edition adds more advanced features.
DDoS detection: Threshold-based alerts on traffic volume. Can detect large floods but lacks dynamic baselines and attack classification.
Strengths: Excellent traffic visibility, protocol-level analysis, web UI.
Limitations for DDoS: No automatic mitigation, no BGP integration, no PCAP forensics triggered by detection.
nfsen / nfdump
nfsen is a web-based front-end for nfdump, the NetFlow/sFlow/IPFIX collector and analyzer. It collects flow data and lets you query and visualize traffic history.
DDoS detection: You can set up alerting profiles that trigger on flow volume thresholds. Detection is delayed by the flow export interval (typically 1-5 minutes).
Strengths: Solid flow collection, good historical analysis, widely used in ISP environments.
Limitations: Dated web interface, no real-time detection, no mitigation integration, manual threshold configuration.
GoFlow2
GoFlow2 is a high-performance NetFlow/sFlow/IPFIX collector written in Go. It ingests flow data and exports to Kafka, databases, or other consumers.
DDoS detection: GoFlow2 itself is a collector, not a detector. You build detection on top of it by consuming the exported data. Useful as a building block but requires custom development for DDoS detection.
Suricata
Suricata is an IDS/IPS with signature-based detection. It can detect some DDoS patterns through rules, but it was designed for intrusion detection, not volumetric DDoS. See our detailed comparison.
Zeek (formerly Bro)
Zeek is a network analysis framework that generates rich logs from network traffic. It provides deep protocol analysis but is designed for security monitoring and forensics, not real-time DDoS detection.
Comparison Table
Tool Type DDoS Focus Mitigation Real-time Cost ----------------------------------------------------------------------- ftagent-lite Monitor Yes No Yes Free NetHawk TUI Analyzer Partial No Yes Free ntopng CE Flow probe Partial No Yes Free nfsen/nfdump Flow collect Partial No Delayed Free GoFlow2 Flow collect No No N/A Free Suricata IDS/IPS No Inline Yes Free Zeek Analysis No No Partial Free
When to Upgrade from Open Source
Open source tools work until they do not. Common upgrade triggers:
- You need automated mitigation: Open source tools detect but do not respond. When an attack hits at 3 AM, you need rules deployed in seconds, not after you SSH in.
- You need attack classification: Knowing "traffic is high" is different from knowing "this is a DNS amplification attack with spoofed sources from port 53."
- You need PCAP evidence: Your ISP, insurance provider, or legal team needs packet captures. Open source tools do not capture PCAPs triggered by detection events.
- You need a multi-node dashboard: Managing 20 servers with 20 separate monitoring tools is unsustainable.
- You need upstream integration: BGP FlowSpec, RTBH, and cloud scrubbing require detection-to-mitigation integration that open source tools do not provide.
Start with ftagent-lite, upgrade when you need more. Install the open source monitor with pip install ftagent. When you need automated mitigation, PCAP forensics, and a multi-node dashboard, upgrade to the full Flowtriq platform. Start your free 14-day trial.