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Upgrade to ProDetect Data Exfiltration via ICMP Covert Channel in Google Chronicle
Tools such as icmpsh, ptunnel, icmptunnel, Nishang's Invoke-PowerShellIcmp, and Cobalt Strike's ICMP beacon exfiltrate collected data by embedding it in the payload of ICMP Echo Request (Type 8) packets and relying on an adversary-controlled listener to reassemble it from Echo Reply traffic. ICMP is exceptionally effective as an exfiltration channel because it is a network-layer control protocol that most firewalls and proxies pass without content inspection or logging, and it requires no application-layer handshake, DNS resolution, or TLS certificate that could be fingerprinted. PLATINUM has been documented using ICMP as a communication and file-transfer channel specifically because it evades traditional network intrusion detection that focuses on TCP/UDP application traffic. Critically, this technique also evades most process-centric EDR network telemetry: Sysmon's Network Connection event (Event ID 3) and Microsoft Defender for Endpoint's DeviceNetworkEvents only monitor TCP/UDP socket activity and do not record raw ICMP traffic at all, so detection here requires visibility from genuinely ICMP-capable network-layer sensors — NGFW/firewall session logs, Zeek/Bro network-tap conn.log, or flow collectors (NetFlow/IPFIX/QFlow). This differs from the generic T1041 base record (which centers on HTTP/DNS beaconing patterns) in that ICMP tunnels are identifiable by a distinct network-layer fingerprint: abnormal session/packet volume to a single destination, oversized payload-per-session inconsistent with diagnostic ping, and sustained session duration outside of standard troubleshooting use.
MITRE ATT&CK
- Tactic
- Exfiltration
YARA-L Detection Query
rule icmp_c2_exfiltration_covert_channel {
meta:
author = "Detection Engineering"
description = "Detects ICMP covert-channel exfiltration via sustained session volume and oversized payload size, sourced from firewall/network telemetry rather than endpoint EDR (which does not capture ICMP)."
mitre_attack_tactic = "Exfiltration"
mitre_attack_technique = "T1041"
severity = "HIGH"
priority = "HIGH"
events:
$e.metadata.event_type = "NETWORK_CONNECTION"
$e.network.ip_protocol = "ICMP"
$e.security_result.action = "ALLOW"
$src = $e.principal.ip
$dst = $e.target.ip
$bytes = $e.network.sent_bytes + $e.network.received_bytes
match:
$src, $dst over 1h
outcome:
$session_count = count($e.metadata.id)
$total_bytes = sum($bytes)
$avg_bytes_per_session = $total_bytes / $session_count
condition:
$e and $session_count >= 200 and $avg_bytes_per_session >= 100
}Chronicle YARA-L 2.0 rule matching NETWORK_CONNECTION UDM events with ip_protocol=ICMP, sourced from firewall/NGFW log forwarders ingested into Chronicle (not endpoint EDR connectors, which do not surface ICMP). Uses match/outcome aggregation over a 1-hour window by source/destination IP pair to score sustained session volume and average payload size per session — the same fingerprint used in the kql/spl scoring model.
Data Sources
Required Tables
False Positives & Tuning
- Network monitoring and availability-check appliances generating sustained ICMP sessions to a small set of anchor IPs
- Path MTU discovery and network troubleshooting using oversized ping payloads
- Authorized vulnerability scanning or network mapping generating high-volume ICMP sweeps
Other platforms for THREAT-ICMP-C2Exfiltration
Testing Methodology
Validate this detection against 2 adversary techniques from Atomic Red Team. Each test below lists the behaviour to exercise and the telemetry you should expect to see. Executable commands and cleanup steps are available with Pro.
- Test 1Simulated ICMP Tunneling via Oversized Ping Payload Burst
Expected signal: CommonSecurityLog (or Zeek conn.log): ~60 permitted ICMP session records between the test host's source IP and 198.51.100.10, each with SentBytes/orig_ip_bytes reflecting the 128-byte payload (well above the 56-byte default), spanning roughly 12 seconds. Sysmon/MDE will NOT show this traffic — that is expected and confirms the endpoint-blind-spot this detection is designed to cover.
- Test 2Sustained Single-Destination ICMP Session Simulation
Expected signal: CommonSecurityLog (or Zeek conn.log): 400 permitted ICMP session records from the test host to 198.51.100.10 spanning approximately 3-4 minutes, with SessionCount and DurationMinutes both elevated relative to normal diagnostic traffic patterns.
References (8)
- https://attack.mitre.org/techniques/T1041/
- https://attack.mitre.org/techniques/T1095/
- https://www.microsoft.com/en-us/security/blog/2017/04/24/platinum-continues-to-evolve-find-ways-to-maintain-invisibility/
- https://github.com/inquisb/icmpsh
- https://github.com/utoni/ptunnel-ng
- https://github.com/samratashok/nishang
- https://github.com/SigmaHQ/sigma/tree/master/rules/network
- https://docs.zeek.org/en/current/scripts/base/protocols/conn/main.zeek.html
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