Detection: Linux Ingress Tool Transfer with Curl

Updated Date: 2026-01-20 ID: 8c1de57d-abc1-4b41-a727-a7a8fc5e0857 Author: Michael Haag, Splunk Type: Anomaly Product: Splunk Enterprise Security

Description

The following analytic detects the use of the curl command with specific switches (-O, -sO, -ksO, --output) commonly used to download remote scripts or binaries. This detection leverages data from Endpoint Detection and Response (EDR) agents, focusing on process names and command-line arguments. This activity is significant as it may indicate an attempt to download and execute potentially malicious files, often used in initial stages of an attack. If confirmed malicious, this could lead to unauthorized code execution, enabling attackers to compromise the system further.

Search

 1
 2| tstats `security_content_summariesonly`
 3  count min(_time) as firstTime
 4        max(_time) as lastTime
 5        
 6from datamodel=Endpoint.Processes where
 7
 8Processes.process_name=curl
 9Processes.process IN ("*-O*","*-sO*","*-ksO*","*--output*")
10by Processes.action Processes.dest Processes.original_file_name
11   Processes.parent_process Processes.parent_process_exec
12   Processes.parent_process_guid Processes.parent_process_id
13   Processes.parent_process_name Processes.parent_process_path
14   Processes.process Processes.process_exec Processes.process_guid
15   Processes.process_hash Processes.process_id
16   Processes.process_integrity_level Processes.process_name
17   Processes.process_path Processes.user Processes.user_id
18   Processes.vendor_product
19
20| `drop_dm_object_name(Processes)`
21
22| `security_content_ctime(firstTime)`
23
24| `security_content_ctime(lastTime)`
25
26| where match(process, "(?i)(-O
27|-sO
28|-ksO
29|--output)")
30
31| `linux_ingress_tool_transfer_with_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_ctime	`convert timeformat="%Y-%m-%dT%H:%M:%S" ctime($field$)`
linux_ingress_tool_transfer_with_curl_filter	`search *`

linux_ingress_tool_transfer_with_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
T1105	Ingress Tool Transfer	Command And Control

Command and Control

DE.AE

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 Risk Event	True

This configuration file applies to all detections of type anomaly. These detections will use Risk Based Alerting.

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 will be present. Tune and then change type to TTP.

Associated Analytic Story

Risk Based Analytics (RBA)

Risk Message:

An instance of $process_name$ was identified on endpoint $dest$ by user $user$ to download a remote file. Review activity for further details.

Risk Object	Risk Object Type	Risk Score	Threat Objects
user	user	12	process_name
dest	system	12	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: 10