Listen to this Post
Introduction
Wireshark is a powerful tool often associated with IT network troubleshooting, but its capabilities extend far beyond—especially in Operational Technology (OT) and Industrial Control Systems (ICS) cybersecurity. Attackers frequently leverage Wireshark for reconnaissance and exploitation, making it critical for defenders to master its features. This article provides actionable Wireshark filters and techniques tailored for OT/ICS environments.
Learning Objectives
- Identify network discovery and suspicious activity in OT/ICS networks.
- Apply protocol-specific filters for Modbus, S7, DNP3, and other industrial protocols.
- Utilize free packet capture resources to practice and refine analysis skills.
1. Network Discovery
Filter: `eth.dst == ff:ff:ff:ff:ff:ff`
Purpose: Identifies broadcast traffic, often used for device discovery.
Steps:
1. Open Wireshark and start a capture.
2. Apply the filter to isolate broadcast frames.
3. Analyze source devices to map network topology.
Filter: `arp.opcode == 2`
Purpose: Captures ARP responses, revealing IP-to-MAC mappings.
Steps:
1. Filter for ARP traffic.
- Look for unsolicited ARP replies, which may indicate spoofing.
Filter: `bootp.option.type == 53`
Purpose: Detects DHCP Discover/Request messages.
Steps:
1. Use the filter to monitor DHCP activity.
2. Identify rogue DHCP servers in OT networks.
2. Detecting Suspicious Activity
Filter: `tcp.flags.syn == 1 && tcp.flags.ack == 0`
Purpose: Flags SYN scans (common in reconnaissance).
Steps:
1. Apply the filter during quiet network periods.
2. Investigate repeated SYN packets from single sources.
Filter: `tcp.dstport < 1 || (tcp.dstport > 1024 && tcp.dstport != 502 && tcp.dstport != 44818)`
Purpose: Highlights connections to unusual ports.
Steps:
- Adjust port numbers based on your environment (e.g., exclude OT protocol ports).
- Flag traffic to non-standard ports for further inspection.
3. Protocol-Specific Filters
Modbus Traffic:
- Filter: `modbus`
Purpose: Isolates Modbus communications.
- Filter: `modbus.func_code == 5`
Purpose: Captures “Write Single Coil” commands, often exploited in attacks.
S7 Traffic:
- Filter: `tcp.port == 102 || s7comm`
Purpose: Monitors Siemens S7 protocol traffic.
DNP3 Traffic:
- Filter: `tcp.port == 20000 || dnp3`
Purpose: Tracks DNP3 protocol activity, common in SCADA systems.
4. Free Packet Capture Resources
Practice with real-world data:
What Undercode Say
Key Takeaway 1: Wireshark is indispensable for OT/ICS defenders but requires protocol-specific knowledge to be effective.
Key Takeaway 2: Attackers use the same tools—proactive monitoring and anomaly detection are critical.
Analysis:
Wireshark’s versatility makes it a double-edged sword. While it helps defenders monitor network integrity, adversaries exploit it for reconnaissance. Organizations must train staff to recognize malicious patterns (e.g., port scans, unexpected protocol commands). The rise of encrypted OT traffic (e.g., over VPNs) complicates analysis, necessitating complementary tools like Zeek or Suricata. Future OT environments will demand deeper integration of Wireshark with IDS/IPS solutions to automate threat detection.
Prediction:
As OT networks converge with IT, Wireshark’s role will expand, but AI-driven analysis tools will augment manual inspection to handle encrypted traffic and large-scale deployments.
IT/Security Reporter URL:
Reported By: Mikeholcomb Think – Hackers Feeds
Extra Hub: Undercode MoN
Basic Verification: Pass ✅
