splunk_escuAnomaly

Non Firefox Process Access Firefox Profile Dir

The following analytic detects non-Firefox processes accessing the Firefox profile directory, which contains sensitive user data such as login credentials, browsing history, and cookies. It leverages Windows Security Event logs, specifically event code 4663, to monitor access attempts. This activity is significant because it may indicate attempts by malware, such as RATs or trojans, to harvest user information. If confirmed malicious, this behavior could lead to data exfiltration, unauthorized access to user accounts, and further compromise of the affected system.

MITRE ATT&CK

T1555.003

Detection Query

`wineventlog_security` EventCode=4663 NOT (ProcessName IN ("*\\firefox.exe", "*\\explorer.exe", "*sql*")) ObjectName="*\\AppData\\Roaming\\Mozilla\\Firefox\\Profiles*" | stats count min(_time) as firstTime max(_time) as lastTime by ObjectName ObjectType ProcessName AccessMask EventCode dest | `security_content_ctime(firstTime)` | `security_content_ctime(lastTime)` | `non_firefox_process_access_firefox_profile_dir_filter`

Author

Teoderick Contreras, Splunk

Created

2026-03-10

Data Sources

Windows Event Log Security 4663

Tags

StealC StealerDarkGate MalwareCISA AA23-347ANjRATPhemedrone StealerAzorultSalt TyphoonRemcosWarzone RATQuasar RAT3CX Supply Chain AttackAgentTeslaRedLine StealerSnappyBeeMalicious Inno Setup LoaderFIN7Snake KeyloggerChina-Nexus Threat Activity0bj3ctivity StealerLokibotBlankGrabber Stealer

Raw Content

name: Non Firefox Process Access Firefox Profile Dir
id: e6fc13b0-1609-11ec-b533-acde48001122
version: 15
date: '2026-03-10'
author: Teoderick Contreras, Splunk
status: production
type: Anomaly
description: The following analytic detects non-Firefox processes accessing the Firefox profile directory, which contains sensitive user data such as login credentials, browsing history, and cookies. It leverages Windows Security Event logs, specifically event code 4663, to monitor access attempts. This activity is significant because it may indicate attempts by malware, such as RATs or trojans, to harvest user information. If confirmed malicious, this behavior could lead to data exfiltration, unauthorized access to user accounts, and further compromise of the affected system.
data_source:
    - Windows Event Log Security 4663
search: '`wineventlog_security` EventCode=4663 NOT (ProcessName IN ("*\\firefox.exe", "*\\explorer.exe", "*sql*")) ObjectName="*\\AppData\\Roaming\\Mozilla\\Firefox\\Profiles*" | stats count min(_time) as firstTime max(_time) as lastTime by ObjectName ObjectType ProcessName AccessMask EventCode dest | `security_content_ctime(firstTime)` | `security_content_ctime(lastTime)` | `non_firefox_process_access_firefox_profile_dir_filter`'
how_to_implement: To successfully implement this search, you must ingest Windows Security Event logs and track event code 4663. For 4663, enable "Audit Object Access" in Group Policy. Then check the two boxes listed for both "Success" and "Failure."
known_false_positives: other browser not listed related to firefox may catch by this rule.
references: []
drilldown_searches:
    - name: View the detection results for - "$dest$"
      search: '%original_detection_search% | search  dest = "$dest$"'
      earliest_offset: $info_min_time$
      latest_offset: $info_max_time$
    - name: View risk events for the last 7 days for - "$dest$"
      search: '| from datamodel Risk.All_Risk | search normalized_risk_object IN ("$dest$") starthoursago=168  | stats count min(_time) as firstTime max(_time) as lastTime values(search_name) as "Search Name" values(risk_message) as "Risk Message" values(analyticstories) as "Analytic Stories" values(annotations._all) as "Annotations" values(annotations.mitre_attack.mitre_tactic) as "ATT&CK Tactics" by normalized_risk_object | `security_content_ctime(firstTime)` | `security_content_ctime(lastTime)`'
      earliest_offset: $info_min_time$
      latest_offset: $info_max_time$
rba:
    message: a non firefox browser process $ProcessName$ accessing $ObjectName$
    risk_objects:
        - field: dest
          type: system
          score: 20
    threat_objects: []
tags:
    analytic_story:
        - StealC Stealer
        - DarkGate Malware
        - CISA AA23-347A
        - NjRAT
        - Phemedrone Stealer
        - Azorult
        - Salt Typhoon
        - Remcos
        - Warzone RAT
        - Quasar RAT
        - 3CX Supply Chain Attack
        - AgentTesla
        - RedLine Stealer
        - SnappyBee
        - Malicious Inno Setup Loader
        - FIN7
        - Snake Keylogger
        - China-Nexus Threat Activity
        - 0bj3ctivity Stealer
        - Lokibot
        - BlankGrabber Stealer
    asset_type: Endpoint
    mitre_attack_id:
        - T1555.003
    product:
        - Splunk Enterprise
        - Splunk Enterprise Security
        - Splunk Cloud
    security_domain: endpoint
tests:
    - name: True Positive Test
      attack_data:
        - data: https://media.githubusercontent.com/media/splunk/attack_data/master/datasets/attack_techniques/T1555/non_chrome_process_accessing_chrome_default_dir/windows-xml.log
          source: XmlWinEventLog:Security
          sourcetype: XmlWinEventLog