---
title: Suspicious Microsoft Antimalware Service Execution
description: Identifies suspicious execution of the Microsoft Antimalware Service Executable (MsMpEng.exe) from non-standard paths or renamed instances. This may indicate...
url: https://www.elastic.co/docs/reference/security/prebuilt-rules/rules/windows/defense_evasion_execution_windefend_unusual_path
products:
  - Elastic Security
---

# Suspicious Microsoft Antimalware Service Execution
Identifies suspicious execution of the Microsoft Antimalware Service Executable (MsMpEng.exe) from non-standard paths or
renamed instances. This may indicate an attempt to evade defenses through DLL side-loading or by masquerading as the
antimalware process.
**Rule type**: eql
**Rule indices**:
- winlogbeat-*
- logs-endpoint.events.process-*
- logs-windows.sysmon_operational-*
- endgame-*
- logs-m365_defender.event-*
- logs-crowdstrike.fdr*

**Rule Severity**: high
**Risk Score**: 73
**Runs every**: 
**Searches indices from**: `now-9m`
**Maximum alerts per execution**: 100
**References**:
- [[https://news.sophos.com/en-us/2021/07/04/independence-day-revil-uses-supply-chain-exploit-to-attack-hundreds-of-businesses/](https://news.sophos.com/en-us/2021/07/04/independence-day-revil-uses-supply-chain-exploit-to-attack-hundreds-of-businesses/)](https://news.sophos.com/en-us/2021/07/04/independence-day-revil-uses-supply-chain-exploit-to-attack-hundreds-of-businesses/)

**Tags**:
- Domain: Endpoint
- OS: Windows
- Use Case: Threat Detection
- Tactic: Defense Evasion
- Data Source: Elastic Endgame
- Data Source: Elastic Defend
- Data Source: Sysmon
- Data Source: Microsoft Defender XDR
- Data Source: Crowdstrike
- Resources: Investigation Guide
- Noise: High
- Performance: Normal
- Profile: Aggressive
- Rule Type: Event Correlation (EQL)
- Platform: Windows

**Version**: 220
**Rule authors**:
- Elastic
- Dennis Perto

**Rule license**: Elastic License v2

## Setup

This rule is designed for data generated by [Elastic Defend](https://www.elastic.co/security/endpoint-security), which provides native endpoint detection and response, along with event enrichments designed to work with our detection rules.
Setup instructions: [https://ela.st/install-elastic-defend](https://ela.st/install-elastic-defend)

### Additional data sources

This rule also supports the following third-party data sources. For setup instructions, refer to the links below:
- [CrowdStrike](https://ela.st/crowdstrike-integration)
- [Microsoft Defender XDR](https://ela.st/m365-defender)
- [Sysmon Event ID 1 - Process Creation](https://ela.st/sysmon-event-1-setup)


## Investigation guide


## Triage and analysis


### Investigating Suspicious Microsoft Antimalware Service Execution


#### Possible investigation steps

- Which Defender identity anomaly did the alert capture?
  - Focus: `process.name`, `process.pe.original_file_name`, `process.executable`, `process.code_signature.subject_name`, and `process.code_signature.trusted`.
  - Implication: escalate when `process.pe.original_file_name` is "MsMpEng.exe" under renamed `process.name`, or `process.name` is "MsMpEng.exe" outside Defender/Microsoft Security Client paths, even with trusted Microsoft signing; lower suspicion only when exact path, signer, and name pattern fit controlled packaging, recovery, or malware-analysis copy.
- Does the path, file timing, and parent context look like staged Defender abuse?
  - Why: unusual-path Defender binaries can load same-folder DLLs through search-order behavior, so path and parent context separate masquerading or side-loading from controlled copies.
  - Focus: `process.executable`, `process.Ext.relative_file_creation_time`, `process.Ext.relative_file_name_modify_time`, `process.parent.executable`, and `process.parent.command_line`.
  - Implication: escalate when the binary is fresh, recently renamed, or launched from user-writable, temp, share, archive, agent working, or Windows staging paths by a script, archive tool, RMM agent, or dropper parent; path age and parent context support benign closure only if later side-loading and launcher checks do not contradict them.
- Does the user, token, and session context fit Defender service execution?
  - Focus: `user.id`, `user.name`, `process.Ext.session_info.logon_type`, and `process.Ext.token.integrity_level_name`.
  - Implication: escalate when the process runs under an interactive/domain user, a non-service logon, or a user-level token that does not fit antimalware service startup; SYSTEM or service context lowers only the session concern and does not clear the unusual path by itself.
- If file or library telemetry is available, is there same-directory staging or DLL side-loading evidence?
  - Focus: recover file and library events with `host.id` plus `process.entity_id` when present, or `host.id` plus `process.pid` and a tight alert window; inspect `file.path`, `dll.path`, `dll.name`, `dll.code_signature.trusted`, and `dll.Ext.relative_file_creation_time`. $investigate_0
  - Hint: missing file or library telemetry is unresolved, not benign; prioritize same-folder DLLs whose path, signer, or creation time does not fit the product layout, plus artifacts created before `process.executable` started.
  - Implication: escalate when the unusual Defender copy loads a recent, unsigned/untrusted same-folder DLL or the directory contains newly staged executables, DLLs, scripts, archives, or renamed files; complete recovery with only expected Microsoft components lowers side-loading concern.
- Does the process act as a launcher rather than a passive service component?
  - Focus: child process events where `process.parent.entity_id` matches suspicious `process.entity_id`, repeated starts from `process.executable` on `host.id`, and child `process.name`, `process.executable`, and `process.command_line`.
    - $investigate_1
    - $investigate_2
  - Implication: escalate when it starts shells, PowerShell, certutil, netsh, installers, encryption tooling, or other hands-on-keyboard utilities, or when repeated launches suggest staged execution; no child or repeat behavior lowers launcher concern but does not clear the path anomaly.
- If local findings stay suspicious or unresolved, do related alerts show path reuse or host compromise?
  - Focus: related alerts for `process.executable`, especially unusual-path Defender, masquerading, or side-loading detections.
    - $investigate_3
  - Hint: also review related alerts for `host.id` or `user.id`, especially staging, persistence, credential-access, ransomware, or other masquerading detections.
    - $investigate_4
    - $investigate_5
  - Implication: broaden scope when the same path appears on unrelated hosts or the host has precursor or follow-on alerts; keep the case local only when related alerts show no reuse or follow-on activity and all local evidence is clean.
- Escalate when Defender identity/path evidence plus one meaningful corroborator supports masquerading or DLL side-loading; close only when exact path, signer, parent, session, host/user scope, and optional outside confirmation tie to one controlled workflow with no contradictory telemetry; preserve artifacts and escalate when findings stay mixed or visibility is incomplete.


### False positive analysis

- A non-default Defender installation, controlled security packaging, recovery, or malware-analysis validation can stage Microsoft antimalware binaries outside default paths. Confirm the same workflow by matching exact `process.executable`, `process.hash.sha256` or `process.code_signature.thumbprint_sha256`, Microsoft `process.code_signature.subject_name`, `process.code_signature.trusted`, `process.parent.executable`, `process.parent.command_line`, `user.id`, `host.id`, and session pattern; without outside records, require recurrence across prior rule alerts without side-loading, launcher, or related-alert contradictions.
- Treat production execution from temp, user-writable, share, archive, agent working, or Windows staging paths as an operational anti-pattern unless a controlled workflow proves why the copy exists. Do not close as benign when same-folder DLLs, child tooling, recent rename timing, or unrelated related alerts contradict it.
- Build exceptions only from the minimum confirmed workflow pattern; avoid exceptions on `process.name`, `process.pe.original_file_name`, signer subject alone, or host alone.


### Response and remediation

- If confirmed benign, reverse any temporary containment and document the exact workflow: executable path, Microsoft signer or hash, parent process, session context, user/host scope, and any controlled packaging, recovery, or lab record that corroborated the telemetry. Create an exception only after the same narrow workflow pattern is stable across prior alerts.
- If suspicious but unconfirmed, preserve the alert details, process tree, command line, binary copy and hash, parent context, directory listing, same-folder DLLs, and related-alert timeline before containment. Apply reversible containment first, such as execution prevention on the suspicious path or temporary host isolation when active launcher behavior or side-loading creates continuing risk and the host role can tolerate interruption.
- If confirmed malicious, preserve process and artifact evidence first, including the suspicious Defender copy, same-folder DLLs, support files, launcher context, and related-alert timeline. Then isolate the host or apply an equivalent endpoint containment control, terminate only the suspicious non-default-path or renamed Defender instance, quarantine the suspicious executable and supporting files, remove launcher or persistence artifacts found during scoping, and restore the legitimate security product from known-good media if the masquerading copy replaced or shadowed a trusted component.
- After containment, restrict execution from user-writable, temporary, share, archive, and agent working directories where feasible, retain process/file/library telemetry that affected this case, and document the confirmed benign workflow or malicious artifact set for future triage.


## Rule Query

```eql
process where host.os.type == "windows" and event.type == "start" and
(
  (process.pe.original_file_name == "MsMpEng.exe" and not process.name : "MsMpEng.exe") or
  (
    process.name : "MsMpEng.exe" and
    not process.executable : (
            "?:\\ProgramData\\Microsoft\\Windows Defender\\*.exe",
            "?:\\Program Files\\Windows Defender\\*.exe",
            "?:\\Program Files (x86)\\Windows Defender\\*.exe",
            "?:\\Program Files\\Microsoft Security Client\\*.exe",
            "?:\\Program Files (x86)\\Microsoft Security Client\\*.exe",

            /* Crowdstrike specific exclusion as it uses NT Object paths */
            "\\Device\\HarddiskVolume*\\ProgramData\\Microsoft\\Windows Defender\\*.exe",
            "\\Device\\HarddiskVolume*\\Program Files\\Windows Defender\\*.exe",
            "\\Device\\HarddiskVolume*\\Program Files (x86)\\Windows Defender\\*.exe",
            "\\Device\\HarddiskVolume*\\Program Files\\Microsoft Security Client\\*.exe",
            "\\Device\\HarddiskVolume*\\Program Files (x86)\\Microsoft Security Client\\*.exe"
    )
  )
)
```

**Framework:** MITRE ATT&CK
- Tactic:
  - Name: Defense Evasion
  - Id: TA0005
  - Reference URL: [[https://attack.mitre.org/tactics/TA0005/](https://attack.mitre.org/tactics/TA0005/)](https://attack.mitre.org/tactics/TA0005/)
- Technique:
  - Name: Masquerading
  - Id: T1036
  - Reference URL: [[https://attack.mitre.org/techniques/T1036/](https://attack.mitre.org/techniques/T1036/)](https://attack.mitre.org/techniques/T1036/)
- Sub Technique:
  - Name: Rename Legitimate Utilities
  - Id: T1036.003
  - Reference URL: [[https://attack.mitre.org/techniques/T1036/003/](https://attack.mitre.org/techniques/T1036/003/)](https://attack.mitre.org/techniques/T1036/003/)
- Sub Technique:
  - Name: Match Legitimate Resource Name or Location
  - Id: T1036.005
  - Reference URL: [[https://attack.mitre.org/techniques/T1036/005/](https://attack.mitre.org/techniques/T1036/005/)](https://attack.mitre.org/techniques/T1036/005/)
- Technique:
  - Name: Hijack Execution Flow
  - Id: T1574
  - Reference URL: [[https://attack.mitre.org/techniques/T1574/](https://attack.mitre.org/techniques/T1574/)](https://attack.mitre.org/techniques/T1574/)
- Sub Technique:
  - Name: DLL
  - Id: T1574.001
  - Reference URL: [[https://attack.mitre.org/techniques/T1574/001/](https://attack.mitre.org/techniques/T1574/001/)](https://attack.mitre.org/techniques/T1574/001/)