Cisco SA - Access to Anonymizer Services

name: Cisco SA - Access to Anonymizer Services
id: a7c8613a-92e2-4232-b64d-bd39d33dee8b
version: 1
creation_date: '2026-05-06'
modification_date: '2026-06-09'
author: Mahamudul Chowdhury, Bhavin Patel, Splunk
status: production
type: Anomaly
description: |
    This analytic detects attempts to access proxy-evasion or anonymizer services using Cisco Secure Access DNS and secure web proxy telemetry.
    Users who reach anonymizer or proxy-evasion infrastructure are often trying to bypass corporate controls such as secure web gateway inspection, DLP monitoring, CASB visibility, and threat-detection systems. These services frequently establish encrypted tunnels that hide subsequent traffic from inspection.
    Early identification helps security teams spot circumvention attempts before potential data exfiltration or follow-on malicious activity. Correlating DNS resolution and proxy session data strengthens confidence that access was intentional.
data_source:
    - Cisco Secure Access DNS
search: |-
    `cisco_secure_access_dns`
    action = "allowed" category= "*anonymizer*"
    | fillnull
    | stats count min(_time) as firstTime max(_time) as lastTime values(domain) as domain values(query) as query values(reply_code) as reply_code values(record_type) as record_type by src_ip src_external_ip user identity_type action category sourcetype
    | `security_content_ctime(firstTime)`
    | `security_content_ctime(lastTime)`
    | `cisco_sa___access_to_anonymizer_services_filter`
how_to_implement: |
    Ingest Cisco Secure Access DNS and proxy events into Splunk using the Splunk Add-on for Cisco Security Cloud (https://splunkbase.splunk.com/app/7404).
    Update the `cisco_secure_access_dns` macro so it resolves to the indexes, sources, and sourcetypes used in your environment.
known_false_positives: |
    Security research, approved privacy tools, or mis-categorized destinations may appear as anonymizer traffic. Tune this analytic with the filter macro or allow-lists for known-good users, networks, and domains after validating business justification.
references:
    - https://attack.mitre.org/techniques/T1090/003
drilldown_searches:
    - name: View the detection results for user $user$ and source $src_ip$
      search: '%original_detection_search% | search user = "$user$" src_ip = "$src_ip$"'
      earliest_offset: $info_min_time$
      latest_offset: $info_max_time$
    - name: View risk events for the last 7 days for $user$
      search: '| from datamodel Risk.All_Risk | search normalized_risk_object IN ("$user$") | 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: 7d
      latest_offset: "0"
intermediate_findings:
    entities:
        - field: user
          type: user
          score: 20
          message: User $user$ from $src_ip$ accessed proxy-evasion or anonymizer infrastructure (domains=$domain$, categories=$category$).
threat_objects:
    - field: domain
      type: domain
analytic_story:
    - Cisco Secure Access Analytics
asset_type: Endpoint
mitre_attack_id:
    - T1090.003
product:
    - Splunk Enterprise
    - Splunk Enterprise Security
    - Splunk Cloud
category: network
security_domain: network
tests:
    - name: True Positive Test - DNS telemetry
      attack_data:
        - data: https://media.githubusercontent.com/media/splunk/attack_data/master/datasets/cisco_secure_access/dns/anonymizer_dns.log
          source: not_applicable
          sourcetype: cisco:cloud_security:dns
      test_type: unit