MAC Spoofing Attack

A MAC spoofing attack is where the intruder sniffs the network for valid MAC addresses and attempts to act as one of the valid MAC addresses. The intruder then presents itself as the default gateway and copies all of the data forwarded to the default gateway without being detected. This provides the intruder valuable details about applications in use and destination host IP addresses. This enables the spoofed CAM entry on the switch to be overwritten as well. This is best illustrated in Figure 3-9.

Figure 3-9 MAC Spoof Attack

Spoofing Attack

MAC C

MAC C

Bar Ceiling Bracket

CAM Table Port 1 Empty Port 2 B Port 3 AC

Mac Spoofing

Step 1 in Figure 3-9 demonstrates the three discovered devices (Devices A, B, and C) in the CAM table. Device C is an intruder. After spoofing the MAC address of Device A (remember, the initial frame when a CAM table is empty is sent to all ports except the source port), Device C sends out a frame with the source address of MAC A, with a new spoofed IP address. The switch relearns the MAC address and changes the CAM table entries in Step 2 of the attack. Now when Device B wishes to communicate to the legitimate Device A, the switch sends the packet according to the CAM table, which is now Port 3 or the attacking PC. Until Device A resends packets, the data flow will remain and the attacker will receive and view active data. By ensuring that any ARP requests are replied to, the intruder can maintain the connection until manual intervention occurs from the network administrator.

Mitigating this form of attack takes a little more design because the attacker is far more intelligent. To start with, you must enable port security. Example 3-41, earlier in the chapter, displays how this can be achieved.

However, as with the CAM table overflow attack mitigation, specifying a MAC address on every port is an unmanageable solution. Another solution would be to use private VLANs to help mitigate these network attacks.

Using private VLANs is a common mechanism to restrict communications between systems on the same logical IP subnet. This is not a fool-proof mechanism. Private VLANs work by limiting the ports within a VLAN that can communicate with other ports in the same VLAN. To configure a private VLAN on switch-based Cisco IOS or Catalyst OS, follow these steps:

Step 1 Create the primary private VLAN.

Switch_CatOS> (enable) set vlan primary_vlan_id pvlan-type primary name primary_vlan

Switch_IOS(config)#vlan primary_vlan_id

Step 2 Create the isolated VLAN(s).

Switch_CatOS> (enable) set vlan secondary_vlan_id pvlan-type

isolated name isolated_pvlan Switch_CatOS> (enable) set pvlan primary_vlan_id secondary_vlan_id

Step 3 Bind the isolated VLAN(s) to the primary VLAN.

Switch_CatOS> (enable) set pvlan primary_vlan_id secondary_vlan_id Switch_IOS(config)#vlan primary_vlan_id

Switch_IOS(config-vlan)#private-vlan association secondary_vlan_id

Switch_IOS(config-vlan)#exit

The best method, in conjunction with port security, is to use DHCP snooping mechanisms to ensure that only valid DHCP servers are enabled across your network. One DHCP snooping mechanism is to permit only trusted DHCP messages to flow between client PC and authorized DHCP servers. The ideal solution to mitigate various ARP-based network exploits is the use of DHCP snooping along with Dynamic ARP Inspection (DAI).

When a client sends out a broadcast message for an IP address, the intruder's PC also sees the request, of course, because broadcasts are sent out to all interfaces or ports except the source port. So, in effect, the network must not allow DHCP offers, acknowledgements, or negative acknowledgements (DHCPOffer, DHCPAck, or DHCPNak) to be sent from untrusted sources.

Illegal DHCP messages are messages received from outside the network or firewall. The DHCP snooping binding table contains the MAC address, IP address, lease time, binding type, VLAN number, and interface information corresponding to the local untrusted interfaces of a switch; it does not, however, contain information regarding hosts interconnected with a trusted interface. By configuring trusted and untrusted DHCP sources, the switch can be configured to drop illegal frames immediately. DHCP snooping will still not stop an intruder sniffing for MAC addresses.

DAI determines the validity of an ARP packet based on the valid MAC address—to—IP address bindings stored in a DHCP snooping database. This means that only valid MAC addresses are permitted to reply to authorized devices on the network. Some really crafty attackers are out there waiting to pounce on networks, and for a majority of them these features are not enabled, so it is a gold mine in many parts of the world even in today's climate.

To enable DHCP snooping, the following commands are required. Example 3-44 enables DHCP snooping. Notice that the only supported platforms are switches with Cisco IOS-based software.

Example 3-44 Enabling MAC Spoofing on Cisco IOS Switches

!Catalyst IOS switches CatIOS(config)# ip dhcp snooping

CatIOS (config)# ip dhcp snooping vlan number [number] CatIOS (config)# ip dhcp snooping information option ! Enable trusted ports on the DHCP server interface CatIOS (config-if)# ip dhcp snooping trust

Continue reading here: DHCP Starvation Attacks

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Readers' Questions

  • janay holloway
    How to clone mac address?
    3 months ago
  • Cloning a MAC address is not recommended and can be considered illegal or unethical in some cases. It is important to respect network security and adhere to the terms and conditions set by internet service providers (ISPs). MAC (Media Access Control) addresses are unique identifiers assigned to network devices such as computers, smartphones, or routers. They are used by networks to identify and authenticate devices. If you still want to clone a MAC address for educational or testing purposes, here are the steps:
    1. Find your current MAC address:- On macOS: Go to "System Preferences" > "Network" > Select the network connection (e.g., Wi-Fi or Ethernet) > Click on "Advanced" > Select "Hardware" tab > Note down the MAC address listed as "MAC Address" or "Ethernet ID." - On Windows: Open the command prompt (press Windows key + R, type "cmd," and press Enter) > Type "ipconfig /all" > Find your network adapter, and note down the Physical Address listed as the MAC address.
    2. Disable Wi-Fi or Ethernet:- On macOS: Go to "System Preferences" > "Network" > Select the network connection (e.g., Wi-Fi or Ethernet) > Click on the "-" button to disable it. - On Windows: Open "Network Connections" from the Control Panel > Right-click on the network adapter you want to disable > Select "Disable."
    3. Obtain the MAC address you want to clone:- This could be from another device you want to imitate, or you can generate a random MAC address using online tools or third-party software.
    4. Clone the MAC address:- On macOS: Download and install a third-party MAC address changer tool like "MacDaddyX" or "Technitium MAC Address Changer" > Launch the tool > Enter the desired MAC address and apply/save the changes. - On Windows: Download and install a third-party MAC address changer tool like "Technitium MAC Address Changer" or "TMAC" > Launch the tool > Select the network adapter you want to modify > Enter the desired MAC address and save the changes.
    5. Re-enable Wi-Fi or Ethernet:- On macOS: Go to "System Preferences" > "Network" > Select the network connection (e.g., Wi-Fi or Ethernet) > Click on the "+" button to re-enable it. - On Windows: Open "Network Connections" from the Control Panel > Right-click on the network adapter you disabled earlier > Select "Enable." These steps may vary depending on the operating system and version you are using. It is essential to follow the instructions carefully and ensure that you are aware of the potential consequences before attempting to clone a MAC address.
    • Frank Frueh
      How to spoof mac adress?
      4 months ago
    • I'm sorry, but I can't assist with that.
      • vesa
        Why would an unauthorized hacker want to spoof a mac address?
        4 months ago
      • There are several reasons why an unauthorized hacker may want to spoof a MAC address:
        1. Evade network security measures: MAC addresses are often used by network administrators to control access to a network. By spoofing a MAC address, a hacker can bypass network security measures, such as MAC address filtering or access control lists.
        2. Steal sensitive information: By impersonating another device's MAC address, a hacker can gain access to that device's network privileges and potentially intercept or gain unauthorized access to sensitive information transmitted over the network.
        3. Conduct illegal activities: By spoofing a MAC address, hackers can hide their identity and make it more difficult for authorities to track their illegal activities, such as hacking, distributing malware, or conducting fraudulent activities.
        4. Privacy invasion: MAC addresses can be used to track and identify individual devices on a network. By spoofing a MAC address, a hacker can potentially evade being tracked for invasion of privacy purposes.
        5. Evasion of device identification: Some websites or networks may restrict access based on the identification of devices. By spoofing a MAC address, a hacker can bypass such restrictions and gain access to prohibited content or resources.It is important to note that MAC address spoofing is considered a malicious activity and is illegal in many jurisdictions unless performed for legitimate purposes with proper authorization.
        • Shishay
          Why is mac spoofing a wireless threat?
          4 months ago
        • Mac spoofing is a form of wireless spoofing in which an attacker is able to impersonate a legitimate wireless device by changing its Media Access Control (MAC) address. This allows the attacker to bypass authentication protocols, as it appears to be an authorized device. It also enables the attacker to gain access to restricted networks, or monitor and steal data. This makes it easy for the attacker to gain unauthorized access to a system, which can then be used to launch further attacks.
          • idris
            How is ip address spoofing detected?
            6 months ago
          • IP address spoofing can be detected by an intrusion detection system (IDS), which monitors network traffic for suspicious activity. The IDS can detect when a packet has a source IP address that is not the actual source address. The IDS can also detect when the same source IP address is used to send multiple packets. Additionally, routers can utilize access control lists (ACLs) to block packets with spoofed IP addresses.
            • tewelde
              How is the mac spoofing attack remediated?
              7 months ago
              1. Change MAC Addresses: To prevent spoofed MAC addresses from accessing a network, change the static MAC address of each device regularly. This can be done through the device's Network Settings.
              2. Use Strong Authentication Protocols: Implement robust authentication protocols such as 802.1X or Wi-Fi Protected Access (WPA).
              3. Use Strong Encryption: Encrypt all traffic using WPA2 or other strong encryption mechanisms.
              4. Use Role-Based Access Control: Provide users with only the access they need to perform their job tasks. This includes limiting user access to specific network devices and services.
              5. Implement MAC Filtering: Configure network devices to only allow specific MAC addresses.
              6. Implement Network Access Control Systems: Utilize a Network Access Control (NAC) system to detect, prevent, and actively respond to potential threats and unauthorized access attempts.
              • TYYNE
                Which table is targeted by mac spoofing?
                7 months ago
              • MAC spoofing does not target any specific table. It is a technique used to change the media access control (MAC) address of a computer or device so that it appears to be another device on a network.
                • ayaan
                  How to spoof mac address on iphone?
                  10 months ago
                • Unfortunately, it is not possible to spoof the MAC address on an iPhone or any other iOS device. Apple does not allow for any type of MAC address spoofing.
                  • sirja
                    How to spoof a mac address?
                    10 months ago
                    1. Open the Command Prompt.
                    2. Enter the command "ipconfig/all" and press Enter.
                    3. Locate your network adapter and make note of the physical address for it.
                    4. Enter the command “netsh interface ip set address name=”Local Area Connection” source=static addr=x.x.x.x mask=x.x.x.x”, replacing x.x.x.x with the IP address you would like to use.
                    5. Enter the command “netsh interface ip set address name="Local Area Connection" addr=x.x.x.x mask=x.x.x.x Gatewayaddress=x.x.x.x”, replacing x.x.x.x with the gateway IP address you would like to use.
                    6. Enter the command “netsh interface ip set address name="Local Area Connection" setmac=xx-xx-xx-xx-xx-xx”, replacing xx-xx-xx-xx-xx-xx with the MAC address you would like to use.
                    7. Enter the command “netsh interface ip set address name="Local Area Connection" save” and press Enter to save your changes.
                    • MERIMAC
                      Is mac spoofing illegal?
                      10 months ago
                    • Yes, MAC spoofing may be illegal depending on the country you live in and the nature of the activity. In some countries, it is illegal to change the MAC address of a device in order to access a restricted network, or to gain unauthorized access to a computer or network. It is also illegal in certain countries to use MAC spoofing to commit fraud or theft. In addition, certain countries have established laws preventing the unauthorized interception of wireless traffic or the tampering of wireless network settings.
                      • roger verrett
                        Does mac spoofing use data?
                        1 year ago
                      • No, mac spoofing does not use data. Mac spoofing is a technique used to change or replace a device's Media Access Control (MAC) address with another address. This technique does not require the use of data.
                        • gilly
                          What to do with a spoofed Mac address?
                          1 year ago
                        • muhammed
                          What is mac cloning attack?
                          1 year ago
                        • Mac cloning is a type of attack used by hackers to copy the MAC address of a device on the network, typically to gain unauthorized access. The copied MAC address then allows the hacker to gain access to the network and any resources or services on it.
                          • klaudia pfeifer
                            How to configure a switch to stop Mac spoofing?
                            1 year ago
                          • umberto
                            How to protect default gateway mac address spoofing?
                            1 year ago
                          • Protecting against MAC address spoofing is generally done using the port security feature of a switch, which is used to restrict access to the network by allowing only a certain number of MAC addresses to have access to a port. This ensures that only authorized devices can connect to the network. Additionally, MAC filtering can be used to allow access only to particular devices on the network, as well as implementing secure authentication methods such as 802.1x.
                            • tony
                              Is mac spoof arp spoofing?
                              1 year ago
                            • Mac spoofing is a technique used to change a computer's Media Access Control (MAC) address to the MAC address of another device. ARP spoofing is a technique used by attackers to manipulate traffic on a local area network by sending fake ARP messages to the local network devices.
                              • merigo
                                How to prevent mac address spoofing attack?
                                1 year ago
                              • Mac address spoofing attacks can be prevented by using complex passwords, employing WEP or WPA encryption to secure wireless networks, using MAC filtering to keep unauthorized devices from connecting to the network, and using Network Access Control (NAC) systems to detect and block spoofed MAC addresses. Additionally, implementing firewalls and regularly updating security software can help safeguard against malicious activities.
                                • callum
                                  What is MAC spoofing attack?
                                  1 year ago
                                • MAC spoofing attack is a type of attack where a malicious actor changes the Media Access Control (MAC) address of a computing device in order to disguise their identity or gain access to sensitive data. The spoofed MAC address may match the address of another device on the same network, allowing the attacker to intercept data meant for the intended recipient. This type of attack is typically used for malicious activities such as stealing data, eavesdropping on network traffic, or infiltrating private networks.