Detection: Cisco ASA - New Local User Account Created

Updated Date: 2025-11-18 ID: 9c8e4f2a-7d3b-4e5c-8a9f-1b6d4e8c3f5a Author: Nasreddine Bencherchali, Splunk Type: Anomaly Product: Splunk Enterprise Security

Description

This analytic detects creation of new user accounts on Cisco ASA devices via CLI or ASDM. Adversaries may create unauthorized user accounts to establish persistence, maintain backdoor access, or elevate privileges on network infrastructure devices. These rogue accounts can provide attackers with continued access even after initial compromise vectors are remediated. The detection monitors for ASA message ID 502101, which is generated whenever a new user account is created on the device, capturing details including the username, privilege level, and the administrator who created the account. Investigate unexpected account creations, especially those with elevated privileges (level 15), accounts created outside business hours, accounts with suspicious or generic names, or accounts created by non-administrative users.

Search

 1`cisco_asa`
 2message_id IN (502101)
 3
 4| fillnull
 5
 6| stats count earliest(_time) as firstTime
 7        latest(_time) as lastTime
 8        values(action) as action
 9        values(message_id) as message_id
10        values(result) as result
11        values(privilege_level) as privilege_level
12  by host user
13
14| `security_content_ctime(firstTime)`
15
16| `security_content_ctime(lastTime)`
17
18| `cisco_asa___new_local_user_account_created_filter`

Data Source

Name	Platform	Sourcetype	Source
Cisco ASA Logs	Other	`'cisco:asa'`	`'not_applicable'`

Macros Used

Name	Value
cisco_asa	`sourcetype=cisco:asa`
cisco_asa___new_local_user_account_created_filter	`search *`

cisco_asa___new_local_user_account_created_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
T1136.001	Local Account	Persistence
T1078.003	Local Accounts	Defense Evasion

Delivery

Exploitation

Installation

DE.AE

CIS 13

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 Risk Event	True

This configuration file applies to all detections of type anomaly. These detections will use Risk Based Alerting.

Implementation

This search requires Cisco ASA syslog data to be ingested into Splunk via the Cisco Security Cloud TA. To ensure this detection works effectively, configure your ASA and FTD devices to generate and forward message ID 502101. If your logging level is set to 'Notifications' or higher, these messages should already be included, else we recommend setting an event list that keeps the severity level you are using and adds message ID 502101. You can find specific instructions on how to set this up here : https://www.cisco.com/c/en/us/support/docs/security/pix-500-series-security-appliances/63884-config-asa-00.html. You can also change the severity level of the above message id's to the syslog level you have currently enabled using the logging message syslog_id level severity_level command in global configuration mode. For more information, see Change the Severity Level of a Syslog Message : https://www.cisco.com/c/en/us/td/docs/security/asa/asa922/configuration/general/asa-922-general-config/monitor-syslog.html#ID-2121-000006da

Known False Positives

Legitimate account creation occurs during employee onboarding, contractor provisioning, service account setup, or emergency access. Verify against HR records and change management tickets. Filter known admin accounts during business hours.

Associated Analytic Story

Suspicious Cisco Adaptive Security Appliance Activity

Risk Based Analytics (RBA)

Risk Message:

New local user account $user$ with privilege level $privilege_level$ was created on Cisco ASA host $host$.

Risk Object	Risk Object Type	Risk Score	Threat Objects
host	system	40	No Threat Objects
user	user	40	No Threat Objects

References

https://www.cisco.com/c/en/us/td/docs/security/asa/syslog/asa-syslog/syslog-messages-500000-to-520025.html#con_4773963

Detection Testing

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

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