Detection: Linux Proxy Socks Curl

Updated Date: 2026-05-13 ID: bd596c22-ad1e-44fc-b242-817253ce8b08 Author: Michael Haag, Splunk, 0xC0FFEEEE, Github Community Type: TTP Product: Splunk Enterprise Security

Description

The following analytic detects the use of the curl command with proxy-related arguments such as -x, socks, --preproxy, and --proxy. This detection leverages data from Endpoint Detection and Response (EDR) agents, focusing on command-line executions and process details. This activity is significant as it may indicate an adversary attempting to use a proxy to evade network monitoring and obscure their actions. If confirmed malicious, this behavior could allow attackers to bypass security controls, making it difficult to track their activities and potentially leading to unauthorized data access or exfiltration.

Search

 1
 2| tstats `security_content_summariesonly` count min(_time) as firstTime max(_time) as lastTime FROM datamodel=Endpoint.Processes
 3  WHERE Processes.process_name=curl Processes.process IN ("*-x *", "*socks4a://*", "*socks5h://*", "*socks4://*","*socks5://*", "*--preproxy *", "--proxy*")
 4  BY Processes.action Processes.dest Processes.original_file_name
 5     Processes.parent_process Processes.parent_process_exec Processes.parent_process_guid
 6     Processes.parent_process_id Processes.parent_process_name Processes.parent_process_path
 7     Processes.process Processes.process_exec Processes.process_guid
 8     Processes.process_hash Processes.process_id Processes.process_integrity_level
 9     Processes.process_name Processes.process_path Processes.user
10     Processes.user_id Processes.vendor_product
11
12| `drop_dm_object_name(Processes)`
13
14| `security_content_ctime(firstTime)`
15
16| `security_content_ctime(lastTime)`
17
18| where match(process, "-x\s") OR match(process, "(?i)socks\d\w?:\/\/
19
20| --(pre)?proxy")
21
22| `linux_proxy_socks_curl_filter`

Data Source

Name	Platform	Sourcetype	Source
Sysmon for Linux EventID 1	Linux	`'sysmon:linux'`	`'Syslog:Linux-Sysmon/Operational'`

Macros Used

Name	Value
security_content_summariesonly	`summariesonly=`summariesonly_config `allow_old_summaries=`oldsummaries_config `fillnull_value=`fillnull_config``
linux_proxy_socks_curl_filter	`search *`

linux_proxy_socks_curl_filter is an empty macro by default. It allows the user to filter out any results (false positives) without editing the SPL.

Annotations

- MITRE ATT&CK

+ Kill Chain Phases

+ NIST

+ CIS

- Threat Actors

ID	Technique	Tactic
T1090	Proxy	Command and Control
T1095	Non-Application Layer Protocol	Command and Control

Command and Control

DE.CM

CIS 10

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 Finding (Notable)	Yes
Rule Title	`%name%`
Rule Description	`%description%`
Notable Event Fields	user, dest
Creates Intermediate Finding (Risk Event)	Yes

TTP detections generate a Finding (Notable) and may generate Intermediate Findings (Risk Events) for associated entities.

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

False positives may be present based on proxy usage internally. Filter as needed.

Associated Analytic Story

Finding

Title	Entity Field	Entity Type	Risk Score
An instance of $process_name$ was identified on endpoint $dest$ by user $user$ utilizing a proxy. Review activity for further details.	user	user	50

Intermediate Findings

Message	Entity Field	Entity Type	Risk Score
An instance of $process_name$ was identified on endpoint $dest$ by user $user$ utilizing a proxy. Review activity for further details.	dest	system	50

Threat Objects

Field	Type
process_name	process_name

References

Detection Testing

Test Type	Status	Dataset	Source	Sourcetype
Validation	✅ Passing	N/A	N/A	N/A
Unit	✅ Passing	Dataset	`Syslog:Linux-Sysmon/Operational`	`sysmon:linux`
Integration	✅ Passing	Dataset	`Syslog:Linux-Sysmon/Operational`	`sysmon:linux`

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: 13