Detect Software Download To Network Device

name: Detect Software Download To Network Device
id: cc590c66-f65f-48f2-986a-4797244762f8
version: 9
creation_date: '2020-10-28'
modification_date: '2026-05-13'
author: Mikael Bjerkeland, Splunk
status: experimental
type: TTP
description: The following analytic identifies unauthorized software downloads to network devices via TFTP, FTP, or SSH/SCP. It detects this activity by analyzing network traffic events on specific ports (69, 21, 22) from devices categorized as network, router, or switch. This activity is significant because adversaries may exploit netbooting to load unauthorized operating systems, potentially compromising network integrity. If confirmed malicious, this could lead to unauthorized control over network devices, enabling further attacks, data exfiltration, or persistent access within the network.
data_source: []
search: |-
    | tstats `security_content_summariesonly` count min(_time) as firstTime max(_time) as lastTime FROM datamodel=Network_Traffic
      WHERE (
            All_Traffic.transport=udp
            AND
            All_Traffic.dest_port=69
        )
        OR (All_Traffic.transport=tcp AND All_Traffic.dest_port=21) OR (All_Traffic.transport=tcp AND All_Traffic.dest_port=22) AND All_Traffic.dest_category!=common_software_repo_destination AND All_Traffic.src_category=network OR All_Traffic.src_category=router OR All_Traffic.src_category=switch
      BY All_Traffic.src All_Traffic.dest All_Traffic.dest_port
    | `drop_dm_object_name("All_Traffic")`
    | `security_content_ctime(firstTime)`
    | `security_content_ctime(lastTime)`
    | `detect_software_download_to_network_device_filter`
how_to_implement: This search looks for Network Traffic events to TFTP, FTP or SSH/SCP ports from network devices. Make sure to tag any network devices as network, router or switch in order for this detection to work. If the TFTP traffic doesn't traverse a firewall nor packet inspection, these events will not be logged. This is typically an issue if the TFTP server is on the same subnet as the network device. There is also a chance of the network device loading software using a DHCP assigned IP address (netboot) which is not in the Asset inventory.
known_false_positives: This search will also report any legitimate attempts of software downloads to network devices as well as outbound SSH sessions from network devices.
references: []
finding:
    title: Potentially unauthorized software download to $dest$
    entity:
        field: dest
        type: system
        score: 50
analytic_story:
    - Router and Infrastructure Security
asset_type: Infrastructure
mitre_attack_id:
    - T1542.005
product:
    - Splunk Enterprise
    - Splunk Enterprise Security
    - Splunk Cloud
category: network
security_domain: network