The following analytic identifies the use of
svc-exe with Cobalt Strike. The behavior typically follows after an adversary has already gained initial access and is escalating privileges. Using
svc-exe, a randomly named binary will be downloaded from the remote Teamserver and placed on disk within
C:\Windows\400619a.exe. Following, the binary will be added to the registry under key
HKLM\System\CurrentControlSet\Services\400619a\ with multiple keys and values added to look like a legitimate service. Upon loading,
services.exe will spawn the randomly named binary from
\\127.0.0.1\ADMIN$\400619a.exe. The process lineage is completed with
400619a.exe spawning rundll32.exe, which is the default
spawnto_ value for Cobalt Strike. The
spawnto_ value is arbitrary and may be any process on disk (typically system32/syswow64 binary). The
spawnto_ process will also contain a network connection. During triage, review parallel procesess and identify any additional file modifications.
- Type: TTP
- Product: Splunk Enterprise, Splunk Enterprise Security, Splunk Cloud
- Datamodel: Endpoint
- Last Updated: 2021-05-18
- Author: Michael Haag, Splunk
- ID: c448488c-b7ec-11eb-8253-acde48001122
Kill Chain Phase
1 2 3 4 5 6 | tstats `security_content_summariesonly` count min(_time) as firstTime max(_time) as lastTime from datamodel=Endpoint.Processes where Processes.parent_process_name=services.exe Processes.process_path=*admin$* by Processes.dest Processes.user Processes.parent_process 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)` | `services_escalate_exe_filter`
The SPL above uses the following Macros:
services_escalate_exe_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
To successfully implement this search, you will need to ensure that DNS data is populating the Network_Resolution data model.
Known False Positives
False positives should be limited as
services.exe should never spawn a process from
ADMIN$. Filter as needed.
Associated Analytic Story
|76.0||80||95||A service process $parent_process_name$ with process path $process_path$ in host $dest$|
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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