Component Object Model Hijackingedit

Identifies Component Object Model (COM) hijacking via registry modification. Adversaries may establish persistence by executing malicious content triggered by hijacked references to COM objects.

Rule type: eql

Rule indices:


Severity: medium

Risk score: 47

Runs every: 5m

Searches indices from: now-9m (Date Math format, see also Additional look-back time)

Maximum alerts per execution: 100



  • Elastic
  • Host
  • Windows
  • Threat Detection
  • Persistence

Version: 7

Rule authors:

  • Elastic

Rule license: Elastic License v2

Investigation guideedit

## Triage and analysis

### Investigating Component Object Model Hijacking

Adversaries can insert malicious code that can be executed in place of legitimate software through hijacking the COM references and relationships as a means of persistence.

#### Possible investigation steps

- Investigate the process execution chain (parent process tree) for unknown processes. Examine their executable files
for prevalence, whether they are located in expected locations, and if they are signed with valid digital signatures.
- Identify the user account that performed the action and whether it should perform this kind of action.
- Investigate other alerts associated with the user/host during the past 48 hours.
- Assess whether this behavior is prevalent in the environment by looking for similar occurrences across hosts.
- Retrieve the file referenced in the registry and determine if it is malicious:
  - Use a private sandboxed malware analysis system to perform analysis.
    - Observe and collect information about the following activities:
      - Attempts to contact external domains and addresses.
      - File and registry access, modification, and creation activities.
      - Service creation and launch activities.
      - Scheduled tasks creation.
  - Use the PowerShell Get-FileHash cmdlet to get the files' SHA-256 hash values.
    - Search for the existence and reputation of the hashes in resources like VirusTotal, Hybrid-Analysis, CISCO Talos,, etc.

### False positive analysis

- Some Microsoft executables will reference the LocalServer32 registry key value for the location of external COM objects.

### Response and remediation

- Initiate the incident response process based on the outcome of the triage.
- Isolate the involved host to prevent further post-compromise behavior.
- If the triage identified malware, search the environment for additional compromised hosts.
  - Implement temporary network rules, procedures, and segmentation to contain the malware.
  - Stop suspicious processes.
  - Immediately block the identified indicators of compromise (IoCs).
  - Inspect the affected systems for additional malware backdoors like reverse shells, reverse proxies, or droppers that
  attackers could use to reinfect the system.
- Remove and block malicious artifacts identified during triage.
- Investigate credential exposure on systems compromised or used by the attacker to ensure all compromised accounts are
identified. Reset passwords for these accounts and other potentially compromised credentials, such as email, business
systems, and web services.
- Run a full antimalware scan. This may reveal additional artifacts left in the system, persistence mechanisms, and
malware components.
- Determine the initial vector abused by the attacker and take action to prevent reinfection through the same vector.
- Using the incident response data, update logging and audit policies to improve the mean time to detect (MTTD) and the
mean time to respond (MTTR).

## Config

If enabling an EQL rule on a non-elastic-agent index (such as beats) for versions <8.2, events will not define `event.ingested` and default fallback for EQL rules was not added until 8.2, so you will need to add a custom pipeline to populate `event.ingested` to @timestamp for this rule to work.

Rule queryedit

registry where
 (registry.path : "HK*}\\InprocServer32\\" and ("scrobj.dll", "C:\\*\\scrobj.dll") and
 not registry.path : "*\\{06290BD*-48AA-11D2-8432-006008C3FBFC}\\*")
 /* in general COM Registry changes on Users Hive is less noisy and worth alerting */
 (registry.path : ("HKEY_USERS\\*Classes\\*\\InprocServer32\\",
                   "HKEY_USERS\\*Classes\\CLSID\\*\\ScriptletURL\\") and
 not (process.executable : "?:\\Program Files*\\Veeam\\Backup and Replication\\Console\\" and
      registry.path : "HKEY_USERS\\S-1-5-21-*_Classes\\CLSID\\*\\LocalServer32\\") and
 /* not necessary but good for filtering privileged installations */
 user.domain != "NT AUTHORITY"
 ) and
 /* removes false-positives generated by OneDrive and Teams */
 not : ("OneDrive.exe","OneDriveSetup.exe","FileSyncConfig.exe","Teams.exe") and
 /* Teams DLL loaded by regsvr */
 not ( "regsvr32.exe" and : "*Microsoft.Teams.*.dll")