Posted in Security

 MAC spoofing and ARP poisoning.

MAC spoofing is using configuration controls to set a different MAC address for a router or laptop so it appears to the network as a device which is known. It used to be that this was required to put a router instead of a PC on a ISP connection – because it was locked down to a specific PC and the ISP would charge extra for each additional MAC address which appeared to be connected. Connecting a router was completely forbidden.

ARP poisoning is where you have a program which is actively sending out unsolicited ARP packets on the network to try to capture the traffic for a device. By altering the ARP table in other devices on the network, they can be forced to send traffic to a monitoring device instead of a router, for example. An ARP cache is used to translate between an IP address and a MAC address on a local network.


  1. Staying anonymous on the network: consider a situation when you are spoofing an ip address in a network. But before that you must have authenticated to the network using a MAC address (which hasn’t changed even after changing your ip address to spoofed one). So, a person intercepting the network can easily find out who you really are by looking at the MAC addresses.
  2. Device Identification: Many airport Wi-Fi networks and other public Wi-Fi networks use a device’s MAC address to identify it. For example, an airport Wi-Fi network might offer a free 30 minutes and then ban your MAC address from receiving more Wi-Fi. Change your MAC address and you may get more Wi-Fi.
  3. MAC filtering: Many networks employ MAC address filtering, only allowing devices with specific MAC addresses to connect to a network. Spoofing an allowed MAC address may give you access to the network.
  4. MAC Authentication: In many colleges and institutions only one device per person is allowed to access the free wifi. This restriction may be based on MAC address filtering, so spoofing the MAC address may allow to use more than one devices when you are allowed to use just one.
  5. Device Tracking: Many free wifi companies may use MAC address to track your movements. Randomizing your mac address may help prevent this type of tracking.



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