ID | Technique | Tactic |
---|---|---|
T1055 | Process Injection | Defense Evasion |
Detection: DLLHost with no Command Line Arguments with Network
EXPERIMENTAL DETECTION
This detection status is set to experimental. The Splunk Threat Research team has not yet fully tested, simulated, or built comprehensive datasets for this detection. As such, this analytic is not officially supported. If you have any questions or concerns, please reach out to us at research@splunk.com.
Description
The following analytic detects instances of DLLHost.exe running without command line arguments while establishing a network connection. This behavior is identified using Endpoint Detection and Response (EDR) telemetry, focusing on process execution and network activity data. It is significant because DLLHost.exe typically runs with specific arguments, and its absence can indicate malicious activity, such as Cobalt Strike usage. If confirmed malicious, this activity could allow attackers to execute code, move laterally, or exfiltrate data, posing a severe threat to the network's security.
Search
1
2| tstats `security_content_summariesonly` count min(_time) as firstTime max(_time) as lastTime FROM datamodel=Endpoint.Processes where Processes.process_name=dllhost.exe Processes.action!="blocked" by host _time span=1h Processes.process_id Processes.process_name Processes.dest Processes.process_path Processes.process Processes.parent_process_name Processes.parent_process
3| `drop_dm_object_name(Processes)`
4| `security_content_ctime(firstTime)`
5| `security_content_ctime(lastTime)`
6| regex process="(?i)(dllhost\.exe.{0,4}$)"
7| rename dest as src
8| join host process_id [
9| tstats `security_content_summariesonly` count latest(All_Traffic.dest) as dest latest(All_Traffic.dest_ip) as dest_ip latest(All_Traffic.dest_port) as dest_port FROM datamodel=Network_Traffic.All_Traffic where All_Traffic.dest_port != 0 by host All_Traffic.process_id
10| `drop_dm_object_name(All_Traffic)`]
11| `dllhost_with_no_command_line_arguments_with_network_filter`
Data Source
Name | Platform | Sourcetype | Source |
---|---|---|---|
Sysmon EventID 1 | Windows | 'xmlwineventlog' |
'XmlWinEventLog:Microsoft-Windows-Sysmon/Operational' |
Sysmon EventID 3 | Windows | 'xmlwineventlog' |
'XmlWinEventLog:Microsoft-Windows-Sysmon/Operational' |
Macros Used
Name | Value |
---|---|
security_content_ctime | convert timeformat="%Y-%m-%dT%H:%M:%S" ctime($field$) |
dllhost_with_no_command_line_arguments_with_network_filter | search * |
dllhost_with_no_command_line_arguments_with_network_filter
is an empty macro by default. It allows the user to filter out any results (false positives) without editing the SPL.
Annotations
Default Configuration
This detection is configured by default in Splunk Enterprise Security to run with the following settings:
Setting | Value |
---|---|
Disabled | true |
Cron Schedule | 0 * * * * |
Earliest Time | -70m@m |
Latest Time | -10m@m |
Schedule Window | auto |
Creates Notable | Yes |
Rule Title | %name% |
Rule Description | %description% |
Notable Event Fields | user, dest |
Creates Risk Event | True |
Implementation
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
Although unlikely, some legitimate third party applications may use a moved copy of dllhost, triggering a false positive.
Associated Analytic Story
Risk Based Analytics (RBA)
Risk Message | Risk Score | Impact | Confidence |
---|---|---|---|
The process $process_name$ was spawned by $parent_process_name$ without any command-line arguments on $src$ by $user$. | 49 | 70 | 70 |
References
Detection Testing
Test Type | Status | Dataset | Source | Sourcetype |
---|---|---|---|---|
Validation | Not Applicable | N/A | N/A | N/A |
Unit | ✅ Passing | Dataset | XmlWinEventLog:Microsoft-Windows-Sysmon/Operational |
XmlWinEventLog |
Integration | ✅ Passing | Dataset | XmlWinEventLog:Microsoft-Windows-Sysmon/Operational |
XmlWinEventLog |
Replay any dataset to Splunk Enterprise by using our replay.py
tool or the UI.
Alternatively you can replay a dataset into a Splunk Attack Range
Source: GitHub | Version: 7