Detection: Cisco Duo Admin Login Unusual Os

Updated Date: 2025-07-10 ID: c4824cc6-d644-458e-a39a-67cd67da75e3 Author: Patrick Bareiss, Splunk Type: TTP Product: Splunk Enterprise Security

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.

Search

1`cisco_duo_activity` "action.name"=admin_login NOT access_device.os IN ("Mac OS X") 
2| rename actor.name as user access_device.ip.address as src_ip 
3| 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 
4| `security_content_ctime(firstTime)` 
5| `security_content_ctime(lastTime)` 
6| `cisco_duo_admin_login_unusual_os_filter`

Data Source

Name	Platform	Sourcetype	Source
Cisco Duo Activity	N/A	`'cisco:duo:activity'`	`'cisco_duo'`

Macros Used

Name	Value
cisco_duo_activity	`sourcetype=cisco:duo:activity`
cisco_duo_admin_login_unusual_os_filter	`search *`

cisco_duo_admin_login_unusual_os_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
T1556	Modify Authentication Process	Credential Access

Exploitation

Installation

DE.CM

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 Notable	Yes
Rule Title	`%name%`
Rule Description	`%description%`
Notable Event Fields	user, dest
Creates Risk Event	True

This configuration file applies to all detections of type TTP. These detections will use Risk Based Alerting and generate Notable Events.

Implementation

The analytic leverages Duo activity logs to be ingested using the Cisco Security Cloud App (https://splunkbase.splunk.com/app/7404).

Known False Positives

unknown

Associated Analytic Story

Cisco Duo Suspicious Activity

Risk Based Analytics (RBA)

Risk Message:

A user $user$ has logged in using an unusual OS $access_device.os$ using browser $access_device.browser$ from $src_ip$.

Risk Object	Risk Object Type	Risk Score	Threat Objects
user	user	48	src_ip, access_device.browser

References

https://splunkbase.splunk.com/app/7404

Detection Testing

Test Type	Status	Dataset	Source	Sourcetype
Validation	✅ Passing	N/A	N/A	N/A
Unit	✅ Passing	Dataset	`duo`	`cisco:duo:activity`
Integration	✅ Passing	Dataset	`duo`	`cisco:duo:activity`

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: 1