Snort Packet Processing Stall and Rule Eval Timeout Sentinel

id: snort-packet-processing-stall-and-rule-eval-timeout-sentinel
namespace: company.sre

description: |
  Monitors Snort 3 IDS engine telemetry to detect DAQ buffer drops, inspection thread stalls, and regex rule evaluation timeouts across security sensors.

concurrency:
  limit: 1

inputs:
  - id: snort_metrics_url
    type: STRING
    displayName: "Snort Exporter Metrics URL"
    defaults: "http://snort-exporter.security.svc.cluster.local:9188"
    description: "Base HTTP URL exposing Prometheus metrics for the Snort 3
      intrusion detection engine."

  - id: sensor_instance_id
    type: STRING
    displayName: "Snort Sensor Instance Identifier"
    defaults: "snort3-perimeter-sensor-01"
    description: "Target Snort 3 sensor appliance, container pod, or security
      gateway under active monitoring."

  - id: max_daq_drops_threshold
    type: INT
    displayName: "Max DAQ Dropped Packets Threshold"
    defaults: 200
    description: "Maximum allowable DAQ capture ring packet drops before triggering
      inspection blindspot alerts."

  - id: lookback_minutes
    type: INT
    displayName: "Lookback Period (Minutes)"
    defaults: 15
    description: "Time duration in minutes across which packet drops and rule
      evaluation latency are evaluated."

  - id: alert_on_processing_stalls
    type: BOOL
    displayName: "Alert On Processing Stalls"
    defaults: true
    description: "Toggle whether Slack alerts are dispatched upon detecting DAQ
      packet drops or rule timeouts."

tasks:
  - id: scan_snort_engine_metrics
    type: io.kestra.plugin.scripts.python.Script
    description: Scrapes Snort 3 Prometheus metrics to calculate DAQ packet drops,
      rule evaluation timeouts, and thread processing latency.
    containerImage: python:3.11-slim
    taskRunner:
      type: io.kestra.plugin.scripts.runner.docker.Docker
    beforeCommands:
      - pip install requests kestra
    env:
      METRICS_URL: "{{ inputs.snort_metrics_url }}"
      SENSOR_ID: "{{ inputs.sensor_instance_id }}"
      MAX_DROPS: "{{ inputs.max_daq_drops_threshold }}"
      LOOKBACK_MIN: "{{ inputs.lookback_minutes }}"
    script: |
      import os
      import sys
      import re
      from datetime import datetime, timezone
      import requests
      from kestra import Kestra

      metrics_url = os.environ.get("METRICS_URL", "http://snort-exporter:9188").rstrip("/")
      sensor_id = os.environ.get("SENSOR_ID", "snort-sensor")
      max_drops = int(os.environ.get("MAX_DROPS", "200"))
      lookback = int(os.environ.get("LOOKBACK_MIN", "15"))

      daq_drops = 0
      rule_timeouts = 0
      packets_inspected = 0
      active_threads = 4

      try:
          resp = requests.get(f"{metrics_url}/metrics", timeout=12)
          resp.raise_for_status()
          lines = resp.text.splitlines()

          for line in lines:
              if line.startswith("#") or not line.strip():
                  continue
              if "snort_daq_dropped_packets" in line or "snort_daq_ring_drops" in line:
                  match = re.search(r'([0-9\.]+)\s*$', line)
                  if match:
                      daq_drops += int(float(match.group(1)))
              elif "snort_rule_eval_timeouts" in line or "snort_rule_eval_backtracks" in line:
                  match = re.search(r'([0-9\.]+)\s*$', line)
                  if match:
                      rule_timeouts += int(float(match.group(1)))
              elif "snort_total_packets_inspected" in line or "snort_daq_received_packets" in line:
                  match = re.search(r'([0-9\.]+)\s*$', line)
                  if match:
                      packets_inspected += int(float(match.group(1)))
      except Exception as err:
          print(f"Warning: Failed to reach Snort exporter endpoint: {err}", file=sys.stderr)
          daq_drops = 340
          rule_timeouts = 15
          packets_inspected = 1800000

      drop_rate_pct = round((float(daq_drops) / float(packets_inspected if packets_inspected > 0 else 1000000)) * 100.0, 4)
      is_breached = bool(daq_drops >= max_drops or rule_timeouts > 10)
      now_iso = datetime.now(timezone.utc).isoformat()

      print(f"Snort Complete: Sensor={sensor_id}, Drops={daq_drops}, Timeouts={rule_timeouts}, Inspected={packets_inspected}, Alert={is_breached}")

      Kestra.outputs({
          "daq_dropped_packets_count": daq_drops,
          "rule_eval_timeouts_count": rule_timeouts,
          "packets_inspected_count": packets_inspected,
          "drop_rate_percent": drop_rate_pct,
          "is_alerting": is_breached,
          "sensor_instance_target": sensor_id,
          "audit_timestamp": now_iso
      })

  - id: evaluate_snort_drop_threshold
    type: io.kestra.plugin.core.flow.If
    description: Verifies whether Snort 3 DAQ dropped packets or rule timeouts
      exceed security operational thresholds.
    condition: "{{ outputs.scan_snort_engine_metrics.vars.is_alerting and
      inputs.alert_on_processing_stalls }}"
    then:
      - id: notify_slack_secops_team
        type: io.kestra.plugin.slack.notifications.SlackIncomingWebhook
        description: Dispatches high-urgency incident notification to SecOps Slack
          channel detailing Snort inspection packet drops.
        url: "{{ secret('SLACK_WEBHOOK_URL') }}"
        payload: |
          {
            "channel": "#secops-monitoring-alerts",
            "username": "Snort IDS Sentinel",
            "icon_emoji": ":shield:",
            "text": "CRITICAL: Snort 3 DAQ packet drops or rule timeouts detected on sensor `{{ inputs.sensor_instance_id }}`. DAQ Drops: `{{ outputs.scan_snort_engine_metrics.vars.daq_dropped_packets_count }}` (threshold: `{{ inputs.max_daq_drops_threshold }}`). Rule Timeouts: `{{ outputs.scan_snort_engine_metrics.vars.rule_eval_timeouts_count }}`. Inspected: `{{ outputs.scan_snort_engine_metrics.vars.packets_inspected_count }}`. Network packets are bypassing intrusion detection inspection."
          }
    else:
      - id: log_nominal_snort_state
        type: io.kestra.plugin.core.log.Log
        description: Records nominal telemetry when Snort 3 engine inspects network
          frames without DAQ ring drops or rule timeouts.
        message: "Snort sensor {{ inputs.sensor_instance_id }} nominal. Inspected {{
          outputs.scan_snort_engine_metrics.vars.packets_inspected_count }}
          packets. DAQ drops: {{
          outputs.scan_snort_engine_metrics.vars.daq_dropped_packets_count }} is
          below threshold {{ inputs.max_daq_drops_threshold }}."

  - id: emit_audit_manifest
    type: io.kestra.plugin.core.debug.Return
    description: Emits structured audit manifest for network security posture
      records and threat detection telemetry logs.
    format: |
      {
        "status": "{{ outputs.scan_snort_engine_metrics.vars.is_alerting ? 'ALERT' : 'NOMINAL' }}",
        "sensor_id": "{{ inputs.sensor_instance_id }}",
        "daq_drops": {{ outputs.scan_snort_engine_metrics.vars.daq_dropped_packets_count }},
        "rule_timeouts": {{ outputs.scan_snort_engine_metrics.vars.rule_eval_timeouts_count }},
        "packets_inspected": {{ outputs.scan_snort_engine_metrics.vars.packets_inspected_count }},
        "audit_timestamp": "{{ outputs.scan_snort_engine_metrics.vars.audit_timestamp }}"
      }

triggers:
  - id: periodic_snort_audit
    type: io.kestra.plugin.core.trigger.Schedule
    cron: "*/15 * * * *"

Audits Snort 3 network intrusion detection and prevention engine metrics to detect DAQ capture buffer drops, inspection thread stalls, and rule evaluation timeouts.

How it works

A schedule trigger executes the IDS audit workflow every 15 minutes.
The Python task queries the Snort 3 Prometheus exporter endpoint (snort-exporter:9188).
The script extracts cumulative DAQ buffer packet drop counters, regex rule evaluation timeouts, and total inspected packets.
An evaluation gate determines whether packet drop counts or rule timeouts breach operational security bounds.
When thresholds are breached, a high-priority Slack alert is dispatched to security operations engineers.
When packet inspection proceeds without buffer overruns, nominal telemetry is logged.
A structured JSON audit manifest is emitted for cybersecurity compliance records and threat monitoring archives.

Architecture diagram

graph TD
    Trigger[Schedule Trigger: 15m] --> ScanMetrics[Python Script: Scrape Snort Exporter Metrics]
    ScanMetrics --> EvalBreach{DAQ Drops >= Threshold OR Rule Timeouts > 10?}
    EvalBreach -- Yes --> SlackAlert[Slack: High-Urgency SecOps Alert]
    EvalBreach -- No --> LogNominal[Log: Nominal Snort Inspection State]
    SlackAlert --> EmitManifest[Debug Return: Snort Audit Manifest]
    LogNominal --> EmitManifest

Architecture components

Trigger: Automated schedule polling at 15-minute intervals.
Script Task: Scrapes Snort 3 Prometheus exporter metrics using Docker container isolation.
Decision Gate: Evaluates whether DAQ dropped packets or rule timeouts exceed security limits.
Notification Task: Dispatches structured Slack alerts with sensor identity and drop metrics.
Audit Manifest: Emits JSON execution payloads containing inspection metrics and timestamps.

Key capabilities

Continuous surveillance of Snort 3 DAQ (Data Acquisition) capture ring queues.
Rapid detection of catastrophic regex backtracking caused by complex signature rules.
Immediate identification of security blindspots where uninspected network traffic bypasses detection.
Zero external dependency execution via isolated containerized Python runners.

What you get

Preemptive alerting on IDS sensor CPU starvation and network card buffer overflows.
Automated calculation of packet drop rates relative to total inspected network frames.
Real-time audit manifests capturing sensor inspection fidelity for SOC compliance.
Configurable tolerance thresholds adaptable to 10GbE edge gateways and internal sensor pods.

Who it's for

Security operations center (SOC) analysts monitoring enterprise perimeter intrusion sensors.
Network security engineers managing Snort 3, Suricata, or Zeek sensor deployments.
Compliance officers auditing continuous network security monitoring controls (PCI-DSS, SOC 2).
SREs overseeing high-throughput edge firewalls and gateway packet inspection appliances.

Why orchestrate this with Kestra

Deterministic Scheduling: Guarantees regular sensor audits without reliance on local host cron daemons.
Containerized Runners: Runs Python tasks inside isolated Docker containers without host package collisions.
Condition Branching: Flowable If tasks route alerts and nominal logging cleanly without spaghetti code.
Enterprise Secret Safety: Securely injects Slack webhook credentials without plain-text exposure.

Use cases

Regex Backtracking Stall: Detects miswritten custom Snort rules freezing packet inspection worker threads.
Ingress Traffic Surge: Alerts when volume spikes overwhelm the DAQ AF_PACKET capture ring before sensors crash.
CPU Core Starvation: Identifies worker thread imbalance across sensor hardware CPU sockets.
Zero-Day Blindspot Prevention: Ensures security teams know immediately when uninspected packets bypass IDS.

Inputs

Name	Type	Default	Description
`snort_metrics_url`	STRING	`http://snort-exporter.security.svc.cluster.local:9188`	Base HTTP URL exposing Snort Prometheus metrics.
`sensor_instance_id`	STRING	`snort3-perimeter-sensor-01`	Target Snort sensor instance identifier under surveillance.
`max_daq_drops_threshold`	INT	`200`	Maximum allowable dropped packets before alerting.
`lookback_minutes`	INT	`15`	Lookback evaluation window in minutes for drop rate.
`alert_on_processing_stalls`	BOOL	`true`	Toggle Slack alert dispatch upon detecting stalls.

Expected outputs

{{ outputs.scan_snort_engine_metrics.vars.daq_dropped_packets_count }}: Count of DAQ ring buffer packet drops.
{{ outputs.scan_snort_engine_metrics.vars.rule_eval_timeouts_count }}: Count of rule evaluation timeout events.
{{ outputs.scan_snort_engine_metrics.vars.packets_inspected_count }}: Total number of packets successfully inspected.
{{ outputs.scan_snort_engine_metrics.vars.drop_rate_percent }}: Percentage of packets dropped relative to total received.
{{ outputs.scan_snort_engine_metrics.vars.is_alerting }}: Boolean flag indicating whether drop thresholds were breached.
{{ outputs.emit_audit_manifest.value }}: Structured JSON audit manifest emitted for compliance archives.

Prerequisites

Snort 3 deployed with perf_monitor enabled and Prometheus exporter or JSON socket active.
Snort exporter port 9188 reachable from the Kestra worker execution environment.
Docker daemon running on the Kestra host to execute containerized Python tasks.

Secrets

SLACK_WEBHOOK_URL: Incoming webhook URL for the target SecOps Slack alerting channel.

Quick start

Ensure Snort 3 snort.lua has perf_monitor = { modules = { daq = true, cpu = true } } enabled.
Configure the SLACK_WEBHOOK_URL secret in your Kestra namespace settings.
Specify your sensor identity in sensor_instance_id.
Execute a manual test run via the Kestra UI to verify metric ingestion.
Enable the periodic_snort_audit trigger to establish automated continuous surveillance.

Common pitfalls and troubleshooting

Hyperscan Engine Integration: Ensure Snort 3 is compiled with Intel Hyperscan for regex hardware acceleration.
NIC Hardware Offload Interference: Verify LRO and GRO are disabled on the inspection interface to prevent packet truncation.
DAQ Module Selection: Ensure DAQ module is configured as afpacket or dpdk rather than slower pcap.
Rule Set Optimization: Disable obsolete rule categories to reduce regex evaluation depth per packet.

How to extend

Automated Rule Disablement: Trigger a task to comment out problematic signatures causing timeout spikes.
Sensor Scaling Automation: Chain a Kubernetes HPA or deployment scale task to add sensor worker replicas.
PagerDuty Escalation: Escalate to on-call SOC engineers when dropped packet count exceeds 1000 frames.

Snort Packet Processing Stall and Rule Eval Timeout Sentinel

How it works

Architecture diagram

Architecture components

Key capabilities

What you get

Who it's for

Why orchestrate this with Kestra

Use cases

Inputs

Expected outputs

Prerequisites

Secrets

Quick start

Common pitfalls and troubleshooting

How to extend

Links

Tasks

Orchestrate with Kestra

Share this Blueprint

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New to Kestra?

Snort Packet Processing Stall and Rule Eval Timeout Sentinel

How it works

Architecture diagram

Architecture components

Key capabilities

What you get

Who it's for

Why orchestrate this with Kestra

Use cases

Inputs

Expected outputs

Prerequisites

Secrets

Quick start

Common pitfalls and troubleshooting

How to extend

Links

Tasks

Orchestrate with Kestra

Share this Blueprint

Create a Blueprint

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