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analyzing-network-flow-data-with-netflow

Parse NetFlow v9 and IPFIX records to detect volumetric anomalies, port scanning, data exfiltration, and C2 beaconing patterns. Uses the Python netflow library to decode flow records, builds traffic baselines, and applies statistical analysis to identify flows with abnormal byte counts, connection durations, and periodic timing patterns.

Published by mukul975 ↗mukul975/Anthropic-Cybersecurity-Skills

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analyzing-network-flow-data-with-netflow

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Use analyzing-network-flow-data-with-netflow to analyze [authorized NetFlow/IPFIX data] in [test or lab environment] and produce prioritized findings for scanning, exfiltration, C2 beaconing, and volumetric anomalies.

Required inputs

  • [authorized NetFlow/IPFIX data]
  • [test or lab environment]

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SKILL.md

name: analyzing-network-flow-data-with-netflowdescription: Parse NetFlow v9 and IPFIX records to detect volumetric anomalies, port  scanning, data exfiltration, and C2 beaconing patterns. Uses the Python netflow  library to decode flow records, builds traffic baselines, and applies statistical  analysis to identify flows with abnormal byte counts, connection durations, and  periodic timing patterns.domain: cybersecuritysubdomain: network-securitytags: - analyzing- network- flow- dataversion: '1.0'author: mahipallicense: Apache-2.0nist_csf: - PR.IR-01- DE.CM-01- ID.AM-03- PR.DS-02mitre_attack: - T1071- T1048- T1046- T1095

Analyzing Network Flow Data with Netflow

When to Use

  • When investigating security incidents that require analyzing network flow data with netflow
  • When building detection rules or threat hunting queries for this domain
  • When SOC analysts need structured procedures for this analysis type
  • When validating security monitoring coverage for related attack techniques

Prerequisites

  • Familiarity with network security concepts and tools
  • Access to a test or lab environment for safe execution
  • Python 3.8+ with required dependencies installed
  • Appropriate authorization for any testing activities

Instructions

  1. Install dependencies: pip install netflow
  2. Collect NetFlow/IPFIX data from routers or use the built-in collector: python -m netflow.collector -p 9995
  3. Parse captured flow data using netflow.parse_packet().
  4. Analyze flows for:
    • Port scanning: single source to many destinations on same port
    • Data exfiltration: high byte-count outbound flows to unusual destinations
    • C2 beaconing: periodic connections with consistent intervals
    • Volumetric anomalies: traffic spikes beyond baseline thresholds
  5. Generate a prioritized findings report.
python scripts/agent.py --flow-file captured_flows.json --output netflow_report.json

Examples

Parse NetFlow v9 Packet

import netflow
data, _ = netflow.parse_packet(raw_bytes, templates={})
for flow in data.flows:
    print(flow.IPV4_SRC_ADDR, flow.IPV4_DST_ADDR, flow.IN_BYTES)