Detect Rogue DHCP Server

name: Detect Rogue DHCP Server
id: 6e1ada88-7a0d-4ac1-92c6-03d354686079
version: 10
creation_date: '2020-08-11'
modification_date: '2026-05-13'
author: Mikael Bjerkeland, Splunk
status: experimental
type: TTP
description: The following analytic identifies the presence of unauthorized DHCP servers on the network. It leverages logs from Cisco network devices with DHCP Snooping enabled, specifically looking for events where DHCP leases are issued from untrusted ports. This activity is significant because rogue DHCP servers can facilitate Man-in-the-Middle attacks, leading to potential data interception and network disruption. If confirmed malicious, this could allow attackers to redirect network traffic, capture sensitive information, and compromise the integrity of the network.
data_source:
    - Cisco IOS Logs
search: |-
    `cisco_networks` facility="DHCP_SNOOPING" mnemonic="DHCP_SNOOPING_UNTRUSTED_PORT"
      | stats min(_time) AS firstTime max(_time) AS lastTime count values(message_type) AS message_type values(src_mac) AS src_mac
        BY host
      | `security_content_ctime(firstTime)`
      | `security_content_ctime(lastTime)`
      | `detect_rogue_dhcp_server_filter`
how_to_implement: This search uses a standard SPL query on logs from Cisco Network devices. The network devices must be configured with DHCP Snooping enabled (see https://www.cisco.com/c/en/us/td/docs/switches/lan/catalyst2960x/software/15-0_2_EX/security/configuration_guide/b_sec_152ex_2960-x_cg/b_sec_152ex_2960-x_cg_chapter_01101.html) and log with a severity level of minimum "5 - notification". The search also requires that the Cisco Networks Add-on for Splunk (https://splunkbase.splunk.com/app/1467) is used to parse the logs from the Cisco network devices.
known_false_positives: This search might be prone to high false positives if DHCP Snooping has been incorrectly configured or in the unlikely event that the DHCP server has been moved to another network interface.
references: []
finding:
    title: DHCP Snooping detected by $host$
    entity:
        field: host
        type: system
        score: 50
analytic_story:
    - Router and Infrastructure Security
    - Scattered Lapsus$ Hunters
asset_type: Infrastructure
mitre_attack_id:
    - T1200
    - T1498
    - T1557
product:
    - Splunk Enterprise
    - Splunk Enterprise Security
    - Splunk Cloud
category: network
security_domain: network