Detection: Cisco TFTP Server Configuration for Data Exfiltration

Updated Date: 2025-08-21 ID: 1abce487-f480-4d5f-a551-01de0bece0bd Author: Bhavin Patel, Michael Haag, Splunk Type: TTP Product: Splunk Enterprise Security

Description

This analytic detects the configuration of TFTP services on Cisco IOS devices that could be used to exfiltrate sensitive configuration files. Threat actors like Static Tundra have been observed configuring TFTP servers to make device configuration files accessible for exfiltration after gaining initial access. The detection specifically looks for commands that expose critical configuration files such as startup-config, running-config, and other sensitive system information through TFTP. This activity is particularly concerning as it may represent an attempt to steal credentials, network topology information, and other sensitive data stored in device configurations.

Search

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="*tftp-server*") AND ( All_Changes.command="*nvram:startup-config*" OR All_Changes.command="*bootflash:running-config*" OR All_Changes.command="*system:running-config*" OR All_Changes.command="*bootflash:info*" OR All_Changes.command="*startup-config*" OR All_Changes.command="*running-config*" ) 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_tftp_server_configuration_for_data_exfiltration_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_tftp_server_configuration_for_data_exfiltration_filter	`search *`

cisco_tftp_server_configuration_for_data_exfiltration_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
T1567	Exfiltration Over Web Service	Exfiltration
T1005	Data from Local System	Collection

Actions on Objectives

Exploitation

DE.CM

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 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

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 command logging events (PARSER-5-CFGLOG_LOGGEDCMD). Configure command logging on Cisco IOS devices using the "archive log config logging enable" command.

Known False Positives

Legitimate TFTP server configurations may be detected by this analytic during authorized backup operations or device maintenance. Network administrators sometimes use TFTP for legitimate configuration backups, firmware updates, or during troubleshooting. To reduce false positives, consider implementing a baseline of expected administrative activities, including approved administrative usernames and scheduled maintenance windows.

Associated Analytic Story

Cisco Smart Install Remote Code Execution CVE-2018-0171

Risk Based Analytics (RBA)

Risk Message:

Suspicious TFTP server configuration detected on Cisco device $dest$ by user $user$, potentially exposing sensitive configuration files

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