Suspicious Image Creation In Appdata Folder

SPLUNK detection rule by Teoderick Contreras, Splunk · Apache-2.0

The following analytic detects the creation of image files in the AppData folder by processes that also have a file reference in the same folder. It leverages data from the Endpoint.Processes and Endpoint.Filesystem datamodels to identify this behavior. This activity is significant because it is commonly associated with malware, such as the Remcos RAT, which captures screenshots and stores them in the AppData folder before exfiltrating them to a command-and-control server. If confirmed malicious, this activity could indicate unauthorized data capture and exfiltration, compromising sensitive information and user privacy.

name: Suspicious Image Creation In Appdata Folder
id: f6f904c4-1ac0-11ec-806b-acde48001122
version: 13
creation_date: '2021-09-22'
modification_date: '2026-05-13'
author: Teoderick Contreras, Splunk
status: production
type: TTP
description: The following analytic detects the creation of image files in the AppData folder by processes that also have a file reference in the same folder. It leverages data from the Endpoint.Processes and Endpoint.Filesystem datamodels to identify this behavior. This activity is significant because it is commonly associated with malware, such as the Remcos RAT, which captures screenshots and stores them in the AppData folder before exfiltrating them to a command-and-control server. If confirmed malicious, this activity could indicate unauthorized data capture and exfiltration, compromising sensitive information and user privacy.
data_source:
    - Sysmon EventID 1 AND Sysmon EventID 11
search: '| tstats `security_content_summariesonly` count FROM datamodel=Endpoint.Processes where Processes.process_name=*.exe Processes.process_path="*\\appdata\\Roaming\\*" by _time span=1h Processes.action Processes.dest Processes.original_file_name Processes.parent_process Processes.parent_process_exec Processes.parent_process_guid Processes.parent_process_id Processes.parent_process_name Processes.parent_process_path Processes.process Processes.process_exec Processes.process_guid Processes.process_hash Processes.process_id Processes.process_integrity_level Processes.process_name Processes.process_path Processes.user Processes.user_id Processes.vendor_product | `drop_dm_object_name(Processes)` |rename process_guid as proc_guid |join proc_guid, _time [| tstats `security_content_summariesonly` count min(_time) as firstTime max(_time) as lastTime FROM datamodel=Endpoint.Filesystem where Filesystem.file_name IN ("*.png","*.jpg","*.bmp","*.gif","*.tiff") Filesystem.file_path= "*\\appdata\\Roaming\\*" by _time span=1h Filesystem.dest Filesystem.file_create_time Filesystem.file_name Filesystem.file_path Filesystem.process_guid | `drop_dm_object_name(Filesystem)` |rename process_guid as proc_guid | fields _time dest file_create_time file_name file_path process_name process_path process proc_guid] | `suspicious_image_creation_in_appdata_folder_filter`'
how_to_implement: To successfully implement this search, you need to be ingesting logs with the process name, parent process, and command-line executions from your endpoints. If you are using Sysmon, you must have at least version 6.0.4 of the Sysmon TA.
known_false_positives: No false positives have been identified at this time.
references:
    - https://success.trendmicro.com/dcx/s/solution/1123281-remcos-malware-information?language=en_US
    - https://blog.malwarebytes.com/threat-intelligence/2021/07/remcos-rat-delivered-via-visual-basic/
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 ("$dest$") | 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: 7d
      latest_offset: "0"
finding:
    title: Process $process_name$ creating image file $file_path$ on $dest$
    entity:
        field: dest
        type: system
        score: 50
threat_objects:
    - field: process_name
      type: process_name
analytic_story:
    - Remcos
    - APT37 Rustonotto and FadeStealer
asset_type: Endpoint
mitre_attack_id:
    - T1113
product:
    - Splunk Enterprise
    - Splunk Enterprise Security
    - Splunk Cloud
category: endpoint
security_domain: endpoint
tests:
    - name: True Positive Test
      attack_data:
        - data: https://media.githubusercontent.com/media/splunk/attack_data/master/datasets/malware/remcos/remcos_agent/sysmon.log
          source: XmlWinEventLog:Microsoft-Windows-Sysmon/Operational
          sourcetype: XmlWinEventLog
      test_type: unit

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