The following analytic identifies the decompile parameter with the HTML Help application, HH.exe. This is a uncommon command to see ran and behavior. Most recently this was seen in a APT41 campaign where a CHM file was delivered and a script inside used a technique for running an arbitrary command in a CHM file via an ActiveX object. This unpacks an HTML help file to a specified path for launching the next stage.
- Type: TTP
- Product: Splunk Enterprise, Splunk Enterprise Security, Splunk Cloud
- Datamodel: Endpoint
- Last Updated: 2022-08-31
- Author: Michael Haag, Splunk
- ID: 2acf0e19-4149-451c-a3f3-39cd3c77e37d
Kill Chain Phase
- CIS 10
1 2 3 4 5 6 | tstats `security_content_summariesonly` count min(_time) as firstTime max(_time) as lastTime from datamodel=Endpoint.Processes where `process_hh` Processes.process=*-decompile* by Processes.dest Processes.user Processes.parent_process_name Processes.process_name Processes.process Processes.process_id Processes.parent_process_id | `drop_dm_object_name(Processes)` | `security_content_ctime(firstTime)` | `security_content_ctime(lastTime)` | `windows_system_binary_proxy_execution_compiled_html_file_decompile_filter`
The SPL above uses the following Macros:
windows_system_binary_proxy_execution_compiled_html_file_decompile_filter is a empty macro by default. It allows the user to filter out any results (false positives) without editing the SPL.
List of fields required to use this analytic.
How To Implement
The detection is based on data that originates from Endpoint Detection and Response (EDR) agents. These agents are designed to provide security-related telemetry from the endpoints where the agent is installed. To implement this search, you must ingest logs that contain the process GUID, process name, and parent process. Additionally, you must ingest complete command-line executions. These logs must be processed using the appropriate Splunk Technology Add-ons that are specific to the EDR product. The logs must also be mapped to the
Processes node of the
Endpoint data model. Use the Splunk Common Information Model (CIM) to normalize the field names and speed up the data modeling process.
Known False Positives
False positives should be limited, filter as needed.
Associated Analytic Story
|90.0||100||90||$process_name$ has been identified using decompile against a CHM on $dest$ under user $user$.|
The Risk Score is calculated by the following formula: Risk Score = (Impact * Confidence/100). Initial Confidence and Impact is set by the analytic author.
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