ID: DT166
Created: 21st October 2026
Updated: 21st October 2026
Platforms: Oracle Cloud Infrastructure (OCI)Google Cloud Platform (GCP)Microsoft AzureAmazon Web Services (AWS)AndroidiOSWindowsLinuxMacOS
Contributor: The ITM Team

Duplicate MAC Address Detection

Identify instances where the same Media Access Control (MAC) address is observed across multiple network access ports, wireless access points, or independently identifiable endpoints within overlapping timeframes. Duplicate MAC address activity may indicate that a subject has deliberately spoofed or cloned the MAC address of an authorized device to impersonate its network identity, circumvent network access restrictions, or conceal the presence of unauthorized hardware.

Detection involves correlating network switch forwarding tables, Network Access Control (NAC) session records, wireless association logs, and authentication events to identify conflicting device identities or simultaneous network connections associated with the same MAC address. Particular attention should be given to instances where the duplicated address is associated with an established organizational asset but is subsequently observed on an unexpected network segment, physical switch port, or device presenting different authentication credentials.

Detection Methods

Analyze Switch MAC Address Tables: Collect and correlate MAC address forwarding tables and MAC movement events from managed network switches. Identify instances where the same MAC address is learned on multiple access ports within overlapping timeframes, particularly where the ports terminate in different physical locations or network segments.
Correlate NAC Authentication Sessions: Review NAC and Remote Authentication Dial-In User Service (RADIUS) authentication records for concurrent sessions presenting the same MAC address. Compare authenticated identities, device certificates, Network Access Server (NAS) identifiers, switch ports, VLAN assignments, and session timestamps to identify inconsistencies between the claimed device identity and the endpoint establishing the connection.
Examine Wireless Association Records: Analyze wireless controller and access point logs for the same MAC address appearing in conflicting association sessions. Distinguish legitimate wireless roaming between access points from simultaneous associations that cannot reasonably be attributed to a single physical endpoint.
Compare Endpoint Identity Records: Correlate observed MAC addresses against asset inventories, endpoint management platforms, and known device certificates. Identify cases where the same MAC address is associated with different persistent device identifiers, hardware serial numbers, or managed endpoint records.
Investigate MAC Movement Events: Review repeated or rapid movement of a MAC address between network switch ports, particularly where the movements occur between geographically separated locations or access ports associated with different subjects. Exclude legitimate movement caused by switching topology, virtualization, network bridging, or authorized infrastructure changes.
Correlate DHCP Lease Activity: Examine Dynamic Host Configuration Protocol (DHCP) lease records for conflicting hostnames, client identifiers, or IP address assignments associated with the same MAC address. Compare lease activity against NAC and network forwarding records to identify potential endpoint impersonation.

Detection Logic

Configure Security Information and Event Management (SIEM) correlation rules to identify MAC addresses associated with multiple independently identifiable network connections.

Prioritize alerts where:

The same MAC address is observed in two concurrent authenticated sessions associated with different device identities.
A MAC address belonging to a managed endpoint appears on an unexpected physical access port while the legitimate endpoint remains connected elsewhere.
Repeated MAC movement events occur between unrelated access ports without an identifiable infrastructure explanation.
A duplicated MAC address is associated with conflicting authentication credentials, device certificates, or endpoint management identifiers.
The conflicting device connection results in access to a restricted network segment or another resource not normally accessible to the subject.

Investigative Considerations

A duplicated MAC address does not independently establish deliberate impersonation. Investigators should exclude legitimate causes, including virtual network interfaces, authorized network bridging, wireless roaming, and network infrastructure behavior. Switch forwarding records should also be assessed for MAC flapping, which may arise from network loops or configuration faults.

Where deliberate duplication is suspected, investigators should establish whether two distinct physical endpoints were operational simultaneously and identify the network access location, authenticated identity, and organizational asset associated with each connection.

Network authentication records, physical access logs, endpoint telemetry, and asset issuance records may assist in attributing the unauthorized connection to a subject.

Sections

ID	Name	Description
AF029.008	MAC Address Spoofing	A subject deliberately changes or falsifies the Media Access Control (MAC) address associated with a network interface to conceal the identity of a device, circumvent network access controls, or frustrate the attribution of network activity during an investigation. MAC addresses are used to identify network interfaces within local network environments and are commonly recorded in network infrastructure logs, Dynamic Host Configuration Protocol (DHCP) lease records, wireless authentication systems, and asset management platforms. MAC address spoofing allows a subject to replace the address normally associated with a network interface with an alternative, potentially fabricated address. This may cause network infrastructure to recognize an existing device as a different endpoint or allow an unauthorized device to impersonate an approved network interface. Where investigative processes rely on MAC addresses to correlate network activity with known organizational assets, this manipulation can introduce attribution discrepancies, obscure device continuity, and complicate the reconstruction of events. A subject may use MAC address spoofing to evade device identification, bypass MAC-based access restrictions, or conceal the use of unauthorized hardware. The technique may also be used to impersonate another device, potentially causing network activity to be incorrectly attributed to an unrelated organizational asset or subject. MAC address modification is not inherently malicious. Some operating systems implement MAC address randomization as a privacy feature, and network administrators may legitimately modify interface addresses for troubleshooting or operational requirements. Investigators should establish whether the modification was authorized, whether it departed from established device configurations, and whether it coincided with activity intended to conceal an infringement or frustrate subsequent investigation. Technical Method A MAC address is a link-layer identifier associated with a network interface. Although typically assigned by the manufacturer, the address presented by an interface can often be overridden through operating system settings, network driver configuration, or specialized software. A subject may perform MAC address spoofing through several mechanisms: Operating System Configuration: Modifying network adapter properties or interface settings to assign a different MAC address. Command-Line Utilities: Using native operating system utilities or third-party software to alter the address presented by a network interface. MAC Address Impersonation: Assigning a MAC address associated with another device to misrepresent the identity of the connecting endpoint. MAC Address Rotation: Repeatedly changing the address to disrupt the continuity of network records and complicate the correlation of activity across sessions. Virtual Network Interfaces: Configuring virtual machines or virtual network adapters to present alternative MAC addresses, potentially obscuring the relationship between a physical host and its network activity. The effectiveness of MAC address spoofing depends on the network architecture and enforcement mechanisms in place. While MAC addresses are visible within a local Layer 2 network, they are not generally preserved across routed network boundaries. The technique therefore primarily affects local device identification, network admission, and attribution based on local network telemetry. Investigative Considerations Investigators should examine discrepancies between observed MAC addresses and the identifiers recorded for known organizational assets. Particular attention should be given to changes in device identity that occur shortly before, during, or after a suspected infringement. Relevant forensic artifacts include: DHCP Lease Records: Identify changes in MAC-to-IP address associations, including multiple MAC addresses associated with the same hostname or DHCP client identifier. Wireless Controller Logs: Examine device association histories, authentication events, and changes in the MAC address presented by a connecting endpoint. Network Access Control (NAC) Logs: Identify unknown MAC addresses, unexpected reauthentication events, or attempts to access network resources using identifiers associated with other assets. Endpoint Detection and Response (EDR) Telemetry: Review network adapter configuration changes, relevant process execution, administrative activity, and persistence mechanisms associated with network interface modifications. Asset Inventory Records: Compare observed network identifiers against established device baselines, serial numbers, endpoint management identifiers, and assigned subject records. Switch and Network Infrastructure Logs: Review MAC address table changes, interface associations, and instances where an identical MAC address appears on unexpected switch ports. Investigators should correlate these artifacts against independent identifiers rather than relying solely on a MAC address. Evidence that a device presented a different MAC address does not, by itself, establish that a particular subject performed the modification.