GitHub Repo

Detection: Cisco SNMP Community String Configuration Changes

Updated Date: 2025-08-21 ID: b0ce5521-2533-4f24-b8d5-c2ff977aae08 Author: Bhavin Patel, Michael Haag, Splunk Type: Anomaly Product: Splunk Enterprise Security

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.

1
2| 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 
3| `drop_dm_object_name("All_Changes")` 
4| rename dvc as dest 
5| `security_content_ctime(firstTime)` 
6| `security_content_ctime(lastTime)` 
7| `cisco_snmp_community_string_configuration_changes_filter`

Data Source

Name Platform Sourcetype Source
Cisco IOS Logs N/A 'cisco:ios' 'cisco:ios'

Macros Used

Name Value
security_content_ctime convert timeformat="%Y-%m-%dT%H:%M:%S" ctime($field$)
cisco_snmp_community_string_configuration_changes_filter search *
cisco_snmp_community_string_configuration_changes_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
T1562.001 Disable or Modify Tools Defense Evasion
T1040 Network Sniffing Credential Access
T1552 Unsecured Credentials Discovery
Exploitation
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

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.

Associated Analytic Story

Risk Based Analytics (RBA)

Risk Message:

Suspicious SNMP community string configuration changes detected on Cisco device $dest$ by user $user$, which may indicate persistence establishment

Risk Object Risk Object Type Risk Score Threat Objects
dest system 60 command
user user 40 command

References

Detection Testing

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

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