Cisco SNMP Community String Configuration Changes

name: Cisco SNMP Community String Configuration Changes
id: b0ce5521-2533-4f24-b8d5-c2ff977aae08
version: 6
creation_date: '2025-08-21'
modification_date: '2026-05-13'
author: Bhavin Patel, Michael Haag, Splunk
status: production
type: Anomaly
description: This analytic detects changes to SNMP community strings on Cisco devices, which could indicate an attacker establishing persistence or attempting to extract credentials. After gaining initial access to network devices, threat actors like Static Tundra often modify SNMP configurations to enable unauthorized monitoring and data collection. This detection specifically looks for the configuration of SNMP community strings with read-write (rw) or read-only (ro) permissions, as well as the configuration of SNMP hosts that may be used to exfiltrate data. These activities are particularly concerning as they may represent attempts to establish persistent access or extract sensitive information from compromised devices.
data_source:
    - Cisco IOS Logs
search: |-
    | tstats `security_content_summariesonly` count values(All_Changes.command) as command min(_time) as firstTime max(_time) as lastTime FROM datamodel=Change.All_Changes
      WHERE (
            (All_Changes.command="*snmp-server community*rw*")
            OR
            (All_Changes.command="*snmp-server community*ro*")
            OR
            (All_Changes.command="*snmp-server host*")
        )
      BY All_Changes.dvc All_Changes.user
    | `drop_dm_object_name("All_Changes")`
    | rename dvc as dest
    | `security_content_ctime(firstTime)`
    | `security_content_ctime(lastTime)`
    | `cisco_snmp_community_string_configuration_changes_filter`
how_to_implement: To implement this search, you need to be ingesting Cisco IOS logs with the sourcetype "cisco:ios" and have these logs mapped to the Change datamodel. Ensure that your Cisco IOS devices are configured to send logs to your Splunk environment, with appropriate logging levels enabled to capture configuration commands. Configure command logging on Cisco IOS devices using the "archive log config logging enable" command to ensure that SNMP configuration changes are properly logged.
known_false_positives: Legitimate SNMP configuration changes may trigger this detection during routine network maintenance or initial device setup. Network administrators often need to configure SNMP for monitoring and management purposes. To reduce false positives, consider implementing a baseline of expected administrative activities, including approved administrative usernames, typical times for SNMP configuration changes, and scheduled maintenance windows. You may also want to create a lookup table of approved SNMP hosts and filter out alerts for these destinations.
references:
    - https://blog.talosintelligence.com/static-tundra/
    - https://tools.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-20180328-smi2
    - https://www.cisco.com/c/en/us/td/docs/ios-xml/ios/snmp/command/snmp-cr-book/snmp-s1.html#wp1307296356
intermediate_findings:
    entities:
        - field: dest
          type: system
          score: 20
          message: Suspicious SNMP community string configuration changes detected on Cisco device $dest$ by user $user$, which may indicate persistence establishment
        - field: user
          type: user
          score: 20
          message: Suspicious SNMP community string configuration changes detected on Cisco device $dest$ by user $user$, which may indicate persistence establishment
threat_objects:
    - field: command
      type: command
analytic_story:
    - Cisco Smart Install Remote Code Execution CVE-2018-0171
asset_type: Network
cve:
    - CVE-2018-0171
mitre_attack_id:
    - T1685
    - T1040
    - T1552
product:
    - Splunk Enterprise
    - Splunk Enterprise Security
    - Splunk Cloud
category: network
security_domain: network