2026-07-04 02:13:35
MAC Address Spoofing: How It Works and How to Stop It
MAC spoofing
ARP spoofing
network security
MITM
switch security
What Is MAC Address Spoofing?
MAC address spoofing is a technique where an attacker falsifies the MAC address of a network interface to impersonate a legitimate device.
ip link set eth0 down
ip link set eth0 address 40:6c:8f:18:2c:03
ip link set eth0 up
Switches maintain a CAM table mapping MAC addresses to physical ports. When an attacker sends frames with a spoofed source MAC, the switch updates its CAM table and redirects traffic to the attacker's port.
Attack Scenarios
ARP Spoofing + MAC Spoofing
All victim traffic flows through the attacker — a transparent man-in-the-middle.
CAM Table Flooding
Once the CAM table is full, the switch falls back to hub mode and broadcasts all traffic to all ports.
Defenses
| Defense | Description |
|---|---|
| Dynamic ARP Inspection (DAI) | Validates ARP packets against DHCP snooping bindings |
| Port Security | Limits learned MACs per port |
| 802.1X Authentication | Requires cryptographic identity before network access |
| VLAN Segmentation | Isolates critical devices |
Conclusion
MAC-based access control alone is insufficient. Combine 802.1X, DAI, and continuous traffic analysis for reliable Layer 2 protection.