Which SIEM platforms have a T1542.004 detection rule?

df00tech provides T1542.004 (ROMMONkit) detection queries for 7 SIEM platforms: Microsoft Sentinel / Defender, Splunk, Elastic Security (EQL), IBM QRadar (AQL), Sumo Logic CSE, Google Chronicle / SecOps, CrowdStrike LogScale (CQL).

What data sources are required to detect ROMMONkit (T1542.004)?

Detecting ROMMONkit requires the following data sources: Network Device: Network Device Configuration, Network Traffic: Network Traffic Content, Cisco IOS Syslog, CEF/CommonSecurityLog from Cisco devices.

What severity and confidence is the T1542.004 detection?

The T1542.004 detection is rated critical severity with medium confidence.

What are common false positives for T1542.004?

Common false positives for T1542.004 include: Legitimate ROMMON upgrades performed by network engineering teams during planned maintenance windows — correlate against change management tickets; Authorized IOS image upgrades via TFTP during software lifecycle management cycles that log BOOT variable changes; Network device password recovery procedures using confreg 0x2142 performed by authorized administrators.

T1542.004 IBM QRadar · QRadar

Detect ROMMONkit in IBM QRadar

Adversaries may abuse the ROM Monitor (ROMMON) by loading unauthorized firmware with adversary code to provide persistent access and manipulate Cisco network device behavior in a way that is extremely difficult to detect. ROMMON is a Cisco network device firmware that functions as a boot loader, boot image, or boot helper to initialize hardware and software when the platform is powered on or reset. An adversary may upgrade the ROMMON image locally or remotely via TFTP with adversary code and restart the device to overwrite the existing ROMMON image. This provides persistence that survives IOS upgrades and standard remediation, and has been observed in the wild via the SYNful Knock implant campaign targeting Cisco ISR routers. Because ROMMON executes before the operating system loads, malicious code embedded at this layer can intercept and modify IOS behavior, inject backdoors, and evade integrity checks.

MITRE ATT&CK

Tactic: Defense Evasion Persistence
Technique: T1542 Pre-OS Boot
Sub-technique: T1542.004 ROMMONkit
Canonical reference: https://attack.mitre.org/techniques/T1542/004/

QRadar Detection Query

IBM QRadar (QRadar)

sql

SELECT
  DATEFORMAT(devicetime, 'yyyy-MM-dd HH:mm:ss') AS EventTime,
  sourceip AS DeviceIP,
  "devicehostname" AS DeviceHostname,
  LOGSOURCENAME(logsourceid) AS LogSource,
  CATEGORYNAME(category) AS EventCategory,
  "utf8(payload)" AS RawMessage,
  CASE
    WHEN LOWER("utf8(payload)") MATCHES '.*rommon|rom monitor|bootldr|boot variable|confreg|config-register|0x2142.*' THEN 1
    ELSE 0
  END AS IsRommonChange,
  CASE
    WHEN LOWER("utf8(payload)") MATCHES '.*tftp|copy tftp|archive download-sw|upgrade rom-monitor|upgrade rommon.*' THEN 1
    ELSE 0
  END AS IsTFTPTransfer,
  CASE
    WHEN "utf8(payload)" MATCHES '.*(SYS-5-RELOAD|Reload requested|SYS-6-BOOTTIME).*' THEN 1
    ELSE 0
  END AS IsReload,
  CASE
    WHEN LOWER("utf8(payload)") MATCHES '.*(boot system|boot path-list|startup-config).*' THEN 1
    ELSE 0
  END AS IsBootVarChange,
  (
    CASE WHEN LOWER("utf8(payload)") MATCHES '.*rommon|rom monitor|bootldr|boot variable|confreg|config-register|0x2142.*' THEN 1 ELSE 0 END +
    CASE WHEN LOWER("utf8(payload)") MATCHES '.*tftp|copy tftp|archive download-sw|upgrade rom-monitor|upgrade rommon.*' THEN 1 ELSE 0 END +
    CASE WHEN "utf8(payload)" MATCHES '.*(SYS-5-RELOAD|Reload requested|SYS-6-BOOTTIME).*' THEN 1 ELSE 0 END +
    CASE WHEN LOWER("utf8(payload)") MATCHES '.*(boot system|boot path-list|startup-config).*' THEN 1 ELSE 0 END
  ) AS SuspicionScore
FROM events
WHERE
  devicetime > (NOW() - 86400000)
  AND (
    LOGSOURCETYPENAME(devicetype) ILIKE '%cisco%'
    OR LOGSOURCETYPENAME(devicetype) ILIKE '%syslog%'
    OR LOGSOURCETYPENAME(devicetype) ILIKE '%network%'
  )
  AND (
    LOWER("utf8(payload)") MATCHES '.*rommon|rom monitor|bootldr|boot variable|confreg|config-register|0x2142|0x2100.*'
    OR LOWER("utf8(payload)") MATCHES '.*tftp|copy tftp|archive download-sw|upgrade rom-monitor|upgrade rommon.*'
    OR "utf8(payload)" MATCHES '.*(SYS-5-RELOAD|Reload requested|SYS-6-BOOTTIME).*'
  )
ORDER BY devicetime DESC

critical severity medium confidence

QRadar AQL rule targeting Cisco IOS and generic syslog sources for ROMMONkit (T1542.004) indicators. Scores each event across four dimensions: ROMMON variable manipulation, TFTP firmware transfers, device reload events, and boot path configuration changes. Events with any positive score are surfaced, with the SuspicionScore field enabling downstream correlation rules to fire on multi-indicator events.

Data Sources

Cisco IOS log source (QRadar DSM for Cisco IOS)Syslog generic log sourceCisco ASA log source

Required Tables

events (QRadar normalized event store)

False Positives & Tuning

Planned ROMMON upgrade during a formal change management window — verify against the organization's change calendar before escalating
TFTP-based IOS image distribution from a known software management server (e.g., Cisco Prime Infrastructure, DNA Center) pulling to multiple devices simultaneously
Network monitoring scripts that issue 'show boot' or 'show version' commands via SNMP or CLI, which may log BOOT path-list output matching keyword patterns

Download portable Sigma rule (.yml)

Other platforms for T1542.004

Microsoft Sentinel (KQL) Splunk (SPL) Elastic Security (Elastic) Sumo Logic CSE (Sumo) Google Chronicle (YARA-L) CrowdStrike LogScale (LogScale) All platforms (combined) →

Testing Methodology

Validate this detection against 4 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 1Verify Current ROMMON Version and Boot Variables
Expected signal: Cisco IOS syslog: `%SYS-6-PRIVCMD` (if privilege accounting enabled) for each privileged exec command. TACACS+ accounting records for the enable session and each show command. AAA accounting logs showing the source IP and username. No TFTP or reload events generated.
Test 2TFTP Image Transfer to Network Device (Lab Only)
Expected signal: Cisco IOS syslog: `%TFTP-6-TRANSFER: Received 1234 bytes` or `%COPY-5-UPROMPRMT: 1234 bytes copied in 2.345 secs`. CommonSecurityLog/Syslog in SIEM will show the TFTP transfer message with source IP 192.168.100.99. TACACS+ accounting logs the `copy tftp` command with source IP. NetFlow captures UDP/69 session from 192.168.100.99 to device management IP.
Test 3Configuration Register Modification (Lab Only)
Expected signal: Cisco IOS syslog: `%SYS-5-CONFIG_I: Configured from console by <user> on <terminal>` after the config change. `show bootvar` output includes `Configuration register is 0x2142`. TACACS+ accounting logs the `config-register 0x2142` command. Syslog forwarded to SIEM contains the CONFIG_I message with the configuration terminal session details.
Test 4ROMMON Environment Variable Inspection via ROMMON Prompt (Lab Only)
Expected signal: Cisco IOS syslog before reload: `%SYS-5-RELOAD: Reload requested by <user> on vty0. Reload Reason: Reload command.` After reload: `%SYS-6-BOOTTIME: Time taken to reboot after reload = <seconds> seconds`. TACACS+ logs the `reload` command. Syslog gap during ROMMON phase (ROMMON does not forward syslog). After IOS boots: logging resumes with startup sequence messages.

Last updated: 2026-04-20 Research depth: deep

References (7)

Response Playbook

1. Examine the full command line and decode any Base64 content...
2. Identify the parent process chain and user context...
3. Check for concurrent network connections from the process...

Investigation Guide

Related techniques: T1027, T1105, T1562.001...
Forensic artifacts: PSReadLine history, Prefetch, ScriptBlock logs...

Atomic Red Team Tests

Test 1: Encoded command execution...
Test 2: Download cradle via Net.WebClient...

Unlock Pro Content

Get the full detection package for T1542.004 including response playbook, investigation guide, and atomic red team tests.

Response PlaybookInvestigation GuideHunting QueriesAtomic Red Team TestsTuning Guidance

Detect ROMMONkit in IBM QRadar

MITRE ATT&CK

QRadar Detection Query

Data Sources

Required Tables

False Positives & Tuning

Other platforms for T1542.004

Testing Methodology

Response Playbook

Investigation Guide

Atomic Red Team Tests

Unlock Pro Content

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MITRE ATT&CK

QRadar Detection Query

Data Sources

Required Tables

False Positives & Tuning

Other platforms for T1542.004

Testing Methodology

Unlock Pro Content

Related Detections

Parent Technique

Related Sub-techniques

Related Techniques

Same Tactic: Defense Evasion

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