Maltrail

Maltrail is a network traffic detection system that identifies communication with known malicious infrastructure and reports selected traffic anomalies. It matches domains, URLs, IP addresses, IP:port pairs, and User-Agent values observed on the network against a set of indicators called trails.

A detection is recorded as a single event containing the source, destination, protocol, matched trail, classification, and trail source:

"2026-08-07 09:14:22.117034" gw 10.13.13.2 57809 1.1.1.1 53 UDP DNS malware.bakewithdavid.com "asyncrat (malware)" (static)

Maltrail is designed for indicator-based network monitoring. Its heuristic detections supplement trail matching, but it is not a replacement for endpoint telemetry or a general-purpose intrusion prevention system.

• A full trail build combining more than 3,000 bundled static files, 42 public-feed integrations, and optional operator-supplied trails.
• A multithreaded Rust sensor using libpcap, with optional Linux PACKET_FANOUT capture workers.
• A Python server providing the reporting interface, event intake, and HTTP API.
• Plain-text custom trails and whitelists that can be reviewed and version-controlled.
• Heuristics for scanning, DNS exhaustion, DGA-like lookups, suspicious downloads, proxy probes, suspicious User-Agent values, and related network activity.
• Local event logging, remote Maltrail logging, CEF over syslog, and Logstash JSON output.
• Deployment validation with maltrail-sensor -T and optional Prometheus metrics.

• Architecture
• Performance
• Installation
  • Installer
  • Building from source
  • Systemd
  • Docker
• Configuration
• Trails
• Events and API
• Operations
  • Monitoring
  • Event retention
• Documentation
• Contributing
• Project
  • License
  • Maintainers
  • Sponsors
  • Presentations and publications
  • Derived blacklist
  • Third-party integrations
  • Acknowledgements

Maltrail consists of two independent processes that may run on the same host or on separate hosts:

   ┌──────────┐   events (UDP or file)   ┌──────────┐
   │  sensor  │ ───────────────────────► │  server  │ ◄── browser
   └──────────┘                          └──────────┘
    Rust                                  Python
    libpcap + PACKET_FANOUT               reporting UI + API
    trail matching + heuristics

The sensor captures traffic, performs trail matching and heuristic analysis, and produces events. It can write events locally (LOG_DIR), send them to a remote Maltrail server (LOG_SERVER), or do both. It can also emit CEF over syslog (SYSLOG_SERVER) and JSON to Logstash (LOGSTASH_SERVER).

The server receives and stores remote events, serves locally available event logs, and provides the web interface and API.

Performance depends on processor, traffic composition, trail-set size, capture driver, and network interface. The figures below measure the sensor's packet-processing path in isolation; they are not end-to-end live-capture measurements.

Representative measurements on an AMD Ryzen 7 PRO 4750U with heuristics enabled and a 1.5 million-row trail set:

Offline comparison runs using the same generated capture, configuration, and trail set measured a 14–37× lower steady-state per-packet cost than the retired Python sensor across the tested systems. The comparison tool reports whole-process time separately because trail loading dominates short replays. It also prints event counts; functional parity is tested independently by the parity corpus.

Run the comparison on the target system with:

python3 sensor/tools/bench_compare.py --packets 300000 \
  --trails ~/.maltrail/trails.csv --repeat 3

One capture worker is used by default. Additional workers can increase capture capacity, but Linux flow hashing divides per-source state between workers and therefore reduces the sensitivity of some scan heuristics. In the documented test, 91% of single-worker heuristic alerts remained with two workers, 86% with four, and 65% with eight. Exact trail matching was unchanged. Increase CAPTURE_FANOUT only when capture-drop metrics show that it is necessary.

Benchmark methodology, hardware results, profiler output, memory measurements, and live fanout checks are documented in sensor/docs/REPORT.md.

The installer supports Debian, Ubuntu, Raspberry Pi OS, RHEL, Fedora, and openSUSE:

curl -fsSL https://raw.githubusercontent.com/stamparm/maltrail/master/install.sh | sudo sh

It installs dependencies, creates a managed checkout under /opt/maltrail, verifies the checksum of the prebuilt sensor, creates an unprivileged maltrail account, installs systemd units, prepares the log and state directories, and starts the sensor and server. Re-running the installer upgrades the managed checkout.

Review the script before running it with elevated privileges. From an existing checkout, the dry run shows the commands without changing the system:

sh install.sh --dry-run

Common installer options:

sh install.sh --role sensor      # Install only the sensor
sh install.sh --ref 3.1.1        # Install a release tag instead of master
sh install.sh --no-service       # Install without changing systemd
sh install.sh --dry-run          # Print commands without applying them
sh install.sh --uninstall        # Remove the managed installation; keep logs and state

The dashboard is available at http://127.0.0.1:8338 after installation. Note that the shipped HTTP_ADDRESS is 0.0.0.0, so it is reachable on every interface, not only loopback — and the default credentials are admin / changeme!. Change USERS, and set HTTP_ADDRESS to 127.0.0.1 (or put the server behind a reverse proxy with TLS), before the host is on an untrusted network.

The initial trail build can take several minutes. The sensor does not detect trail matches until a valid trail set is available. The systemd unit runs the sensor's -T validation before startup so that missing privileges, an unwritable log directory, or an invalid trail set causes startup to fail visibly.

The installer test harness covers Ubuntu, Debian, Fedora, openSUSE, and Alpine containers. Alpine uses musl and does not use the prebuilt glibc sensor binary; build the sensor from source there.

The sensor requires Rust 1.74 or newer, libpcap development headers, and the system's capability tools. The server and trail updater require Python 3.6 or newer.

Install the distribution packages:

# Debian / Ubuntu / Raspberry Pi OS
sudo apt-get install cargo libpcap-dev libcap2-bin python3

# RHEL / Fedora
sudo dnf install cargo libpcap-devel libcap python3

# openSUSE / SLES
sudo zypper install cargo rust libpcap-devel libcap-progs python311

Then build and validate the sensor:

git clone --depth 1 https://github.com/stamparm/maltrail.git
cd maltrail

cargo build --release --manifest-path sensor/Cargo.toml

sudo setcap cap_net_raw,cap_net_admin=eip \
  sensor/target/release/maltrail-sensor

sudo install -d -o "$USER" -g "$(id -gn)" -m 750 /var/log/maltrail

sensor/target/release/maltrail-sensor -T
sensor/target/release/maltrail-sensor

Start the server in another terminal or on another host:

python3 server.py

Prebuilt x86_64 and aarch64 sensor binaries are attached to current releases with SHA-256 checksums. They target glibc 2.28 and require libpcap at runtime. On musl-based systems such as Alpine Linux, build from source.

The retired Python sensor is used only by comparison and parity tools. Those tools additionally require pcapy-ng and the Python development headers described in sensor/docs/INSTALL.md.

The supplied maltrail-server.service and maltrail-sensor.service units run both processes as the unprivileged maltrail user. Systemd creates /var/log/maltrail and /var/lib/maltrail, restricts filesystem access, and grants the sensor CAP_NET_RAW and CAP_NET_ADMIN.

The installer configures these units automatically. For an existing source installation, follow the manual service procedure in sensor/docs/INSTALL.md.

Check service state and logs with:

systemctl status maltrail-sensor maltrail-server
journalctl -u maltrail-sensor -f

Start the supplied Compose deployment with:

docker compose -f docker/docker-compose.yml up -d

Container configuration, storage, privileges, and health checks are documented in docker/README.md.

Maltrail reads maltrail.conf, which contains separate [Sensor] and [Server] settings. The installer places the managed configuration at /etc/maltrail.conf.

Frequently used sensor options include:

PROCESS_COUNT applies to the retired Python sensor. Configure the Rust sensor's capture workers with CAPTURE_FANOUT instead.

Run the deployment check after changing configuration:

sensor/target/release/maltrail-sensor -T

The check validates configuration, trails, whitelist entries, capture filter, privileges, log storage, update support, and worker settings. A successful check includes positive trail and whitelist counts rather than only confirming that files exist.

Trails are stored as plain-text indicators:

trails/static/malware/       malware-related static trails
trails/static/malicious/     malicious infrastructure
trails/static/suspicious/    suspicious infrastructure and behavior
trails/feeds/*.py            public feed integrations

Add local indicators under CUSTOM_TRAILS_DIR. Add indicators that should never generate alerts to USER_WHITELIST. Keeping custom data outside the managed checkout prevents upgrades from overwriting it.

The updater rebuilds TRAILS_FILE from enabled feeds, bundled static trails, and custom trails. A new file is published atomically only after a successful build. Empty or failed feeds are reported so that a running deployment does not silently depend on stale or retired sources.

Trail contributions should include the indicator, classification, and a verifiable source. See Contributing before submitting a pull request.

Maltrail records one whitespace-separated event per detection, using CSV quoting where a value contains spaces:

"<time>" <sensor> <src_ip> <src_port> <dst_ip> <dst_port> <proto> <type> <trail> "<info>" <reference>

The type field identifies what matched, including DNS, IP, IPORT, URL, PATH, HTTP, UA, PORT, and CERT. The info field contains the trail classification, and reference identifies the static list, feed, custom source, or heuristic that produced it.

Use /check to query one domain, IP address, or URL:

curl 'http://127.0.0.1:8338/check?q=www.sub.evil.example'

{
  "query": "www.sub.evil.example",
  "found": true,
  "trail": "evil.example",
  "info": "asyncrat (malware)",
  "reference": "(static)"
}

A subdomain lookup can match its listed parent. URL lookups check host/path before checking the host alone. The server reads the memory-mapped trail database and observes trail updates without a restart.

Public static and feed trails are available without authentication, consistent with the /trails endpoint used by remote sensors. Custom trails require an authorized session; an unauthorized custom-only lookup is reported as a miss. Event data remains authenticated.

Use maltrail-sensor -T as a deployment and configuration gate. The supplied systemd unit runs it as ExecStartPre.

When STATS_ADDRESS is configured, monitor at least these Prometheus metrics:

State saturation affects the corresponding heuristic; exact trail matching remains active.

Send SIGHUP or use systemctl reload maltrail-sensor to request a trail reload. Trail files updated by another process are detected automatically and published to workers without restarting the sensor.

The condensed observable store (USE_CONDENSED_STORAGE, meta.sqlite) supports the server's novelty and retro-hunt views. Compatibility with the retired sensor is documented in sensor/docs/COMPATIBILITY.md.

Maltrail does not rotate or delete event logs. Operators are responsible for defining retention, archival, and deletion according to storage requirements and organizational policy.

Recommended practices:

• Send the durable event copy to a remote Maltrail server or SIEM with LOG_SERVER, SYSLOG_SERVER, or LOGSTASH_SERVER.
• Alert on maltrail_log_dir_free_bytes with enough headroom for the expected event rate.
• Rotate, archive, or remove local daily logs using external tooling.
• Keep files needed by the reporting interface uncompressed in LOG_DIR; archive compressed files elsewhere.

When the log filesystem is full, the sensor cannot append events. Event logs may also contain IP addresses and domains that are regulated as personal data in some jurisdictions; retention policy should account for the applicable requirements.

Trail additions, feed maintenance, bug reports, documentation, and sensor improvements are welcome. Trail submissions should include a reliable source and should use the narrowest appropriate classification.

Run the relevant checks before submitting code. The complete sensor gate is:

bash sensor/tools/check.sh

It runs formatting, Clippy with warnings denied, debug and release tests, and parity replay against the retired Python sensor. Run the Python server suite with:

bash tests/run.sh python3

Maltrail is distributed under the MIT License. See LICENSE.

• Miroslav Stampar (@stamparm)
• Mikhail Kasimov (@MikhailKasimov)

• Sansec (2024–2025)
• Sansec (2020–2021)

• 47th TF-CSIRT Meeting, Prague, 2016 (slides)
• Detect attacks on your network with Maltrail, Linux Magazine, 2022 (article)
• Best Cyber Threat Intelligence Feeds, Silent Push, 2022 (review)
• Research on Network Malicious Traffic Detection System Based on Maltrail, Nanotechnology Perceptions, 2024 (paper)

A domain-only list derived from trails/static/malware is published at maltrail-malware-domains.txt. It can be used as an input to DNS filtering systems, but operators should review and test it before enabling blocking. Threat-intelligence lists can contain false positives or indicators that are not appropriate for every environment.

• FreeBSD Port
• OPNsense Gateway Plugin
• D4 Project
• BlackArch Linux
• Validin
• Maltrail Add-on for Splunk
• Maltrail decoder and rules for Wazuh
• GScan (trails only)
• MalwareWorld (trails only)
• oisd domain blocklist (trails only)
• NextDNS (trails only)
• NoTracking (trails only)
• OWASP Mobile Audit (trails only)
• Mobile Security Framework MobSF (trails only)
• pfBlockerNG-devel (trails only)
• Sansec eComscan (trails only)
• Palo Alto Networks Cortex XSOAR (trail connector)

• Thomas Kristner
• Eduardo Arcusa Les
• James Lay
• Ladislav Baco (@laciKE)
• John Kristoff (@jtkdpu)
• Michael Münz (@mimugmail)
• David Brush
• @Godwottery
• Chris Wild (@briskets)
• Keith Irwin (@ki9us)
• Simon Szustkowski (@simonszu)