Name:Linux Proxy Socks Curl id:bd596c22-ad1e-44fc-b242-817253ce8b08 version:8 date:2025-03-27 author:Michael Haag, Splunk, 0xC0FFEEEE, Github Community status:production type:TTP 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. Data_source:
-Sysmon for Linux EventID 1
search:| tstats `security_content_summariesonly` count min(_time) as firstTime max(_time) as lastTime from datamodel=Endpoint.Processes where Processes.process_name=curl Processes.process IN ("*-x *", "*socks4a://*", "*socks5h://*", "*socks4://*","*socks5://*", "*--preproxy *", "--proxy*") by Processes.action Processes.dest Processes.original_file_name Processes.parent_process Processes.parent_process_exec Processes.parent_process_guid Processes.parent_process_id Processes.parent_process_name Processes.parent_process_path Processes.process Processes.process_exec Processes.process_guid Processes.process_hash Processes.process_id Processes.process_integrity_level Processes.process_name Processes.process_path Processes.user Processes.user_id Processes.vendor_product | `drop_dm_object_name(Processes)` | `security_content_ctime(firstTime)` | `security_content_ctime(lastTime)` | where match(process, "-x\s") OR match(process, "(?i)socks\d\w?:\/\/|--(pre)?proxy") | `linux_proxy_socks_curl_filter`
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 may be present based on proxy usage internally. Filter as needed. References: -https://www.offensive-security.com/metasploit-unleashed/proxytunnels/ -https://curl.se/docs/manpage.html -https://en.wikipedia.org/wiki/SOCKS -https://oxylabs.io/blog/curl-with-proxy -https://reqbin.com/req/c-ddxflki5/curl-proxy-server#:~:text=To%20use%20a%20proxy%20with,be%20URL%20decoded%20by%20Curl. -https://gtfobins.github.io/gtfobins/curl/ drilldown_searches: name:'View the detection results for - "$user$" and "$dest$"' search:'%original_detection_search% | search user = "$user$" dest = "$dest$"' earliest_offset:'$info_min_time$' latest_offset:'$info_max_time$' name:'View risk events for the last 7 days for - "$user$" and "$dest$"' search:'| from datamodel Risk.All_Risk | search normalized_risk_object IN ("$user$", "$dest$") starthoursago=168 | stats count min(_time) as firstTime max(_time) as lastTime values(search_name) as "Search Name" values(risk_message) as "Risk Message" values(analyticstories) as "Analytic Stories" values(annotations._all) as "Annotations" values(annotations.mitre_attack.mitre_tactic) as "ATT&CK Tactics" by normalized_risk_object | `security_content_ctime(firstTime)` | `security_content_ctime(lastTime)`' earliest_offset:'$info_min_time$' latest_offset:'$info_max_time$' tags: analytic_story: - 'Linux Living Off The Land' - 'Ingress Tool Transfer' asset_type:Endpoint mitre_attack_id: - 'T1090' - 'T1095' product: - 'Splunk Enterprise' - 'Splunk Enterprise Security' - 'Splunk Cloud' security_domain:endpoint
