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https://github.com/splunk/security_content
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Eric
94 lines
4.8 KiB
YAML
94 lines
4.8 KiB
YAML
name: Linux Proxy Socks Curl
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id: bd596c22-ad1e-44fc-b242-817253ce8b08
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version: 9
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date: '2025-05-02'
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author: Michael Haag, Splunk, 0xC0FFEEEE, Github Community
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status: production
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type: TTP
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description: The following analytic detects the use of the `curl` command with proxy-related
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arguments such as `-x`, `socks`, `--preproxy`, and `--proxy`. This detection leverages
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data from Endpoint Detection and Response (EDR) agents, focusing on command-line
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executions and process details. This activity is significant as it may indicate
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an adversary attempting to use a proxy to evade network monitoring and obscure their
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actions. If confirmed malicious, this behavior could allow attackers to bypass security
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controls, making it difficult to track their activities and potentially leading
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to unauthorized data access or exfiltration.
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data_source:
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- Sysmon for Linux EventID 1
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search: '| tstats `security_content_summariesonly` count min(_time) as firstTime max(_time)
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as lastTime from datamodel=Endpoint.Processes where Processes.process_name=curl
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Processes.process IN ("*-x *", "*socks4a://*", "*socks5h://*", "*socks4://*","*socks5://*",
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"*--preproxy *", "--proxy*") by Processes.action Processes.dest Processes.original_file_name
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Processes.parent_process Processes.parent_process_exec Processes.parent_process_guid
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Processes.parent_process_id Processes.parent_process_name Processes.parent_process_path
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Processes.process Processes.process_exec Processes.process_guid Processes.process_hash
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Processes.process_id Processes.process_integrity_level Processes.process_name Processes.process_path
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Processes.user Processes.user_id Processes.vendor_product | `drop_dm_object_name(Processes)`
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| `security_content_ctime(firstTime)` | `security_content_ctime(lastTime)` | where
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match(process, "-x\s") OR match(process, "(?i)socks\d\w?:\/\/|--(pre)?proxy") |
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`linux_proxy_socks_curl_filter`'
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how_to_implement: The detection is based on data that originates from Endpoint Detection
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and Response (EDR) agents. These agents are designed to provide security-related
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telemetry from the endpoints where the agent is installed. To implement this search,
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you must ingest logs that contain the process GUID, process name, and parent process.
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Additionally, you must ingest complete command-line executions. These logs must
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be processed using the appropriate Splunk Technology Add-ons that are specific to
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the EDR product. The logs must also be mapped to the `Processes` node of the `Endpoint`
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data model. Use the Splunk Common Information Model (CIM) to normalize the field
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names and speed up the data modeling process.
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known_false_positives: False positives may be present based on proxy usage internally.
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Filter as needed.
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references:
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- https://www.offensive-security.com/metasploit-unleashed/proxytunnels/
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- https://curl.se/docs/manpage.html
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- https://en.wikipedia.org/wiki/SOCKS
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- https://oxylabs.io/blog/curl-with-proxy
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- https://reqbin.com/req/c-ddxflki5/curl-proxy-server#:~:text=To%20use%20a%20proxy%20with,be%20URL%20decoded%20by%20Curl.
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- https://gtfobins.github.io/gtfobins/curl/
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drilldown_searches:
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- name: View the detection results for - "$user$" and "$dest$"
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search: '%original_detection_search% | search user = "$user$" dest = "$dest$"'
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earliest_offset: $info_min_time$
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latest_offset: $info_max_time$
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- name: View risk events for the last 7 days for - "$user$" and "$dest$"
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search: '| from datamodel Risk.All_Risk | search normalized_risk_object IN ("$user$",
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"$dest$") starthoursago=168 | stats count min(_time) as firstTime max(_time)
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as lastTime values(search_name) as "Search Name" values(risk_message) as "Risk
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Message" values(analyticstories) as "Analytic Stories" values(annotations._all)
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as "Annotations" values(annotations.mitre_attack.mitre_tactic) as "ATT&CK Tactics"
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by normalized_risk_object | `security_content_ctime(firstTime)` | `security_content_ctime(lastTime)`'
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earliest_offset: $info_min_time$
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latest_offset: $info_max_time$
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rba:
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message: An instance of $process_name$ was identified on endpoint $dest$ by user
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$user$ utilizing a proxy. Review activity for further details.
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risk_objects:
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- field: user
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type: user
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score: 56
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- field: dest
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type: system
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score: 56
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threat_objects:
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- field: process_name
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type: process_name
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tags:
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analytic_story:
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- Linux Living Off The Land
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- Ingress Tool Transfer
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asset_type: Endpoint
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mitre_attack_id:
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- T1090
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- T1095
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product:
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- Splunk Enterprise
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- Splunk Enterprise Security
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- Splunk Cloud
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security_domain: endpoint
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tests:
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- name: True Positive Test
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attack_data:
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- data: https://media.githubusercontent.com/media/splunk/attack_data/master/datasets/attack_techniques/T1105/atomic_red_team/curl-linux-sysmon.log
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source: Syslog:Linux-Sysmon/Operational
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sourcetype: sysmon:linux
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