analyzing-network-traffic-for-incidents

name	analyzing-network-traffic-for-incidents
description	Analyzes network traffic captures and flow data to identify adversary activity during security incidents, including command-and-control communications, lateral movement, data exfiltration, and exploitation attempts. Uses Wireshark, Zeek, and NetFlow analysis techniques. Activates for requests involving network traffic analysis, packet capture investigation, PCAP analysis, network forensics, C2 traffic detection, or exfiltration detection.
domain	cybersecurity
subdomain	incident-response
tags	["network-forensics","PCAP-analysis","Wireshark","Zeek","traffic-analysis"]
version	1.0.0
author	mahipal
license	Apache-2.0

Analyzing Network Traffic for Incidents

When to Use

• SIEM alerts on anomalous network traffic patterns requiring deeper investigation
• C2 beaconing is suspected and needs confirmation through packet-level analysis
• Data exfiltration volume or destination must be quantified from network evidence
• Lateral movement between systems needs to be traced through network connections
• An IDS/IPS alert requires packet-level validation to confirm or dismiss

Do not use for host-based forensic analysis (process execution, file system artifacts); use endpoint forensics tools instead.

Prerequisites

• Full packet capture (PCAP) infrastructure or on-demand capture capability (network tap, SPAN port)
• Wireshark installed on the analysis workstation with appropriate display filters knowledge
• Zeek (formerly Bro) deployed for network metadata generation (conn.log, dns.log, http.log, ssl.log)
• NetFlow/IPFIX collection from network devices for traffic flow analysis
• Network architecture diagram showing VLAN layout, firewall placement, and monitoring points
• Threat intelligence feeds for correlating observed network indicators

Workflow

Step 1: Capture or Acquire Network Traffic

Obtain the relevant traffic data for the investigation:

Live Capture (if incident is active):

# Capture on specific interface filtering by host
tcpdump -i eth0 -w capture.pcap host 10.1.5.42

# Capture C2 traffic to specific external IP
tcpdump -i eth0 -w c2_traffic.pcap host 185.220.101.42

# Capture with rotation (1GB files, keep 10)
tcpdump -i eth0 -w capture_%Y%m%d%H%M.pcap -C 1000 -W 10

From Existing Infrastructure:

• Export PCAP from full packet capture appliance (Arkime/Moloch, ExtraHop, Corelight)
• Pull Zeek logs from the Zeek cluster for the investigation timeframe
• Export NetFlow data from network devices for high-level traffic analysis

Step 2: Identify C2 Communications

Detect command-and-control traffic patterns:

Beaconing Detection (Zeek conn.log):

# Extract connections to external IPs with regular intervals
cat conn.log | zeek-cut ts id.orig_h id.resp_h id.resp_p duration orig_bytes resp_bytes \
  | awk '$4 ~ /^185\.220/' |  -t. -k1,1n -k2,2n