Cisco Duo Admin Login Unusual Os

SPLUNK detection rule by Patrick Bareiss, Splunk · Apache-2.0

The following analytic identifies Duo admin login attempts from operating systems that are unusual for your environment, excluding commonly used OS such as Mac OS X. Please adjust to your environment. It works by analyzing Duo activity logs for admin login actions and filtering out logins from expected operating systems. The analytic then aggregates events by browser, version, source IP, location, and OS details to highlight anomalies. Detecting admin logins from unexpected operating systems is critical for a SOC, as it may indicate credential compromise, unauthorized access, or attacker activity using unfamiliar devices. Such behavior can precede privilege escalation, policy changes, or other malicious actions within the Duo environment. Early detection enables rapid investigation and response, reducing the risk of account takeover and minimizing potential damage to organizational security controls.

name: Cisco Duo Admin Login Unusual Os
id: c4824cc6-d644-458e-a39a-67cd67da75e3
version: 6
creation_date: '2025-07-10'
modification_date: '2026-05-13'
author: Patrick Bareiss, Splunk
status: production
type: TTP
description: The following analytic identifies Duo admin login attempts from operating systems that are unusual for your environment, excluding commonly used OS such as Mac OS X. Please adjust to your environment. It works by analyzing Duo activity logs for admin login actions and filtering out logins from expected operating systems. The analytic then aggregates events by browser, version, source IP, location, and OS details to highlight anomalies. Detecting admin logins from unexpected operating systems is critical for a SOC, as it may indicate credential compromise, unauthorized access, or attacker activity using unfamiliar devices. Such behavior can precede privilege escalation, policy changes, or other malicious actions within the Duo environment. Early detection enables rapid investigation and response, reducing the risk of account takeover and minimizing potential damage to organizational security controls.
data_source:
    - Cisco Duo Activity
search: |-
    `cisco_duo_activity` "action.name"=admin_login NOT access_device.os IN ("Mac OS X")
      | rename actor.name as user access_device.ip.address as src_ip
      | stats count min(_time) as firstTime max(_time) as lastTime
        BY access_device.browser access_device.browser_version src_ip
           access_device.location.city access_device.location.country access_device.location.state
           access_device.os access_device.os_version actor.details
           actor.type outcome.result user
      | `security_content_ctime(firstTime)`
      | `security_content_ctime(lastTime)`
      | `cisco_duo_admin_login_unusual_os_filter`
how_to_implement: The analytic leverages Duo activity logs to be ingested using the Cisco Security Cloud App (https://splunkbase.splunk.com/app/7404).
known_false_positives: No false positives have been identified at this time.
references:
    - https://splunkbase.splunk.com/app/7404
drilldown_searches:
    - name: View the detection results for - "$user$"
      search: '%original_detection_search% | search  user = "$user$"'
      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"
finding:
    title: A user $user$ has logged in using an unusual OS $access_device.os$ using browser $access_device.browser$ from $src_ip$.
    entity:
        field: user
        type: user
        score: 50
threat_objects:
    - field: access_device.browser
      type: http_user_agent
    - field: src_ip
      type: ip_address
analytic_story:
    - Cisco Duo Suspicious Activity
asset_type: Identity
mitre_attack_id:
    - T1556
product:
    - Splunk Enterprise
    - Splunk Enterprise Security
    - Splunk Cloud
category: application
security_domain: identity
tests:
    - name: True Positive Test
      attack_data:
        - data: https://media.githubusercontent.com/media/splunk/attack_data/master/datasets/attack_techniques/T1556/cisco_duo_unusual_admin_login/cisco_duo_activity.json
          source: duo
          sourcetype: cisco:duo:activity
      test_type: unit

[[ currentRule.title && currentRule.title.length > 60 ? currentRule.title.slice(0, 60) + '…' : currentRule.title ]]

4d66a680-9f35-4794-bf94-75055c90b5f2

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Executable code, not a declarative rule

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Not a security issue — this rule is valid and was accepted as-is. These are optional fields/conventions its own format recommends, mainly affecting its quality score and how well it documents itself for other reviewers.

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