Name:Windows MSHTA Writing to World Writable Path id:efbcf8ee-bc75-47f1-8985-a5c638c4faf0 version:3 date:2024-09-30 author:Michael Haag, Splunk status:production type:TTP Description:The following analytic identifies instances of `mshta.exe` writing files to world-writable directories. It leverages Sysmon EventCode 11 logs to detect file write operations by `mshta.exe` to directories like `C:\Windows\Tasks` and `C:\Windows\Temp`. This activity is significant as it often indicates an attempt to establish persistence or execute malicious code, deviating from the utility's legitimate use. If confirmed malicious, this behavior could lead to the execution of multi-stage payloads, potentially resulting in full system compromise and unauthorized access to sensitive information. Data_source:
-Sysmon EventID 11
search:`sysmon` EventCode=11 Image="*\\mshta.exe" TargetFilename IN ("*\\Windows\\Tasks\\*", "*\\Windows\\Temp\\*", "*\\Windows\\tracing\\*", "*\\Windows\\PLA\\Reports\\*", "*\\Windows\\PLA\\Rules\\*", "*\\Windows\\PLA\\Templates\\*", "*\\Windows\\PLA\\Reports\\en-US\\*", "*\\Windows\\PLA\\Rules\\en-US\\*", "*\\Windows\\Registration\\CRMLog\\*", "*\\Windows\\System32\\Tasks\\*", "*\\Windows\\System32\\Com\\dmp\\*", "*\\Windows\\System32\\LogFiles\\WMI\\*", "*\\Windows\\System32\\Microsoft\\Crypto\\RSA\\MachineKeys\\*", "*\\Windows\\System32\\spool\\PRINTERS\\*", "*\\Windows\\System32\\spool\\SERVERS\\*", "*\\Windows\\System32\\spool\\drivers\\color\\*", "*\\Windows\\System32\\Tasks\\Microsoft\\Windows\\RemoteApp and Desktop Connections Update\\*", "*\\Windows\\SysWOW64\\Tasks\\*", "*\\Windows\\SysWOW64\\Com\\dmp\\*", "*\\Windows\\SysWOW64\\Tasks\\Microsoft\\Windows\\PLA\\*", "*\\Windows\\SysWOW64\\Tasks\\Microsoft\\Windows\\RemoteApp and Desktop Connections Update\\*", "*\\Windows\\SysWOW64\\Tasks\\Microsoft\\Windows\\PLA\\System\\*") | rename Computer as dest, User as user | stats count min(_time) as firstTime max(_time) as lastTime by dest, user, Image, TargetFilename | `security_content_ctime(firstTime)` | `security_content_ctime(lastTime)` | `windows_mshta_writing_to_world_writable_path_filter`
how_to_implement:The analytic is designed to be run against Sysmon event logs collected from endpoints. The analytic requires the Sysmon event logs to be ingested into Splunk. The search focuses on EventCode 11 where the Image is `mshta.exe` and the TargetFilename is within world-writable directories such as `C:\Windows\Tasks`, `C:\Windows\Temp`, and others. The detection is designed to catch the initial file write operation by `mshta.exe` to these locations, which is indicative of an attempt to establish persistence or execute malicious code. The analytic can be modified to include additional world-writable directories as needed. known_false_positives:False positives may occur if legitimate processes are writing to world-writable directories. It is recommended to investigate the context of the file write operation to determine if it is malicious or not. Modify the search to include additional known good paths for `mshta.exe` to reduce false positives. References: -https://www.mandiant.com/resources/blog/apt29-wineloader-german-political-parties -https://www.zscaler.com/blogs/security-research/european-diplomats-targeted-spikedwine-wineloader 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:'$info_max_time$' tags: analytic_story: - 'APT29 Diplomatic Deceptions with WINELOADER' - 'Suspicious MSHTA Activity' group: - 'APT29' - 'Cozy Bear' - 'Midnight Blizzard' asset_type:Endpoint confidence:80 impact:80 message:An instance of $Image$ writing to $TargetFilename$ was detected on $dest$. mitre_attack_id: - 'T1218.005' observable: name:'Image' type:'File Name' - role: - 'Attacker' name:'dest' type:'Hostname' - role: - 'Victim' product: - 'Splunk Enterprise' - 'Splunk Enterprise Security' - 'Splunk Cloud' required_fields: - 'dest' - 'user' - 'Image' - 'TargetFilename' risk_score:64 security_domain:endpoint cve:
