What is an ARP Redirect Attack?

An ARP Redirect attack is a form of ARP Spoofing (also known as ARP Poisoning), where an attacker manipulates a victim’s ARP cache table, tricking them into believing that the attacker is the router. This causes the victim’s network traffic to first pass through the attacker before reaching the actual router. The attacker can then sniff, modify, or manipulate the traffic for malicious purposes.

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What is ARP (Address Resolution Protocol)?

ARP (Address Resolution Protocol) is a network protocol used to map an IP address to a physical MAC (Media Access Control) address. Devices in a network need to know the MAC address of the destination device to establish communication, which is achieved through ARP requests and responses.

How ARP Works

ARP Request: A device broadcasts an ARP request to the network, asking for the MAC address of a specific IP address.
ARP Response: The device with the requested IP address replies with its MAC address.
ARP Cache Storage: The requesting device stores the MAC address in its ARP cache for future reference, reducing the need for repeated ARP requests.

How an ARP Redirect Attack Works

An ARP Redirect attack exploits this process by poisoning the ARP cache of a victim. The attacker sends falsified ARP responses to redirect the victim’s traffic through the attacker’s machine before reaching the router.

Attack Process

The attacker sends forged ARP replies to the victim
- The attacker sends a spoofed ARP reply to the victim, associating the router’s IP address with the attacker’s MAC address.
- This tricks the victim into sending all traffic intended for the router to the attacker instead.
The attacker also poisons the router’s ARP cache
- The attacker sends a spoofed ARP reply to the router, associating the victim’s IP address with the attacker’s MAC address.
- This ensures that the router also mistakenly sends traffic to the attacker instead of the legitimate device.
The attacker intercepts and sniffs traffic
- Since both the victim’s and router’s ARP tables are poisoned, all traffic is funneled through the attacker’s device.
- The attacker can then inspect, modify, or drop packets.
Packets are forwarded to the legitimate router
- To avoid detection, the attacker forwards the packets to the actual router after sniffing or modifying them.
- The victim remains unaware that their traffic is being intercepted.

Risks of ARP Redirect Attacks

A successful ARP Redirect attack can result in serious security threats:

Data Sniffing: The attacker can capture sensitive information such as login credentials, emails, and private messages.
Session Hijacking: The attacker can steal session cookies to impersonate the victim and gain unauthorized access to accounts.
Man-in-the-Middle (MITM) Attacks: The attacker can modify traffic to inject malicious code or redirect users to phishing sites.
Denial-of-Service (DoS) Attacks: The attacker can disrupt communication by dropping packets, effectively cutting off network access.

How to Prevent and Mitigate ARP Redirect Attacks

To effectively protect against ARP Redirect attacks, organizations must implement both prevention methods (before an attack occurs) and response strategies (after an attack has been detected).

Prevention Methods (Before an Attack)

Configure Static ARP Entries

Set static ARP entries for critical devices such as routers and servers to prevent unauthorized ARP updates.
On Windows, use arp -s <IP Address> <MAC Address> to manually bind an IP to a MAC address.
On Linux, configure static ARP entries in /etc/ethers to persist even after reboots.

Use ARP Monitoring and Filtering Tools

Deploy tools like arpwatch, ArpON, or XArp to detect and alert network administrators about suspicious ARP changes.
Configure real-time alerts to respond quickly to ARP poisoning attempts.

Enable Security Features on Network Switches

Dynamic ARP Inspection (DAI): Configurable on managed switches to prevent malicious ARP packets.
Port Security: Restricts specific MAC addresses to certain switch ports, preventing unauthorized devices from injecting ARP packets.

Implement Encrypted Communication (VPN & HTTPS)

Encrypt network traffic using SSL/TLS to prevent data theft even if an attacker intercepts packets.
Use VPNs to create a secure communication channel between endpoints.

Use Network Segmentation (VLANs)

Implement VLANs to isolate critical devices from general network traffic, making it harder for attackers to execute ARP poisoning across segments.

Response Strategies (After an Attack is Detected)

Check and Correct the ARP Cache Table

Run arp -a on Windows or ip neigh show on Linux to inspect current ARP cache entries.
If an unauthorized MAC address is associated with an IP, manually delete it using arp -d <IP Address> and reconfigure the correct mapping.

Analyze Network Traffic for Anomalies

Use Wireshark or tcpdump to capture and analyze ARP traffic.
Look for duplicate ARP responses, unexpected MAC address changes, or high volumes of unsolicited ARP packets.

Block the Attacker and Restore Network Integrity

Identify the attacker’s MAC address and block it using firewall rules or network ACLs.
Restart network equipment such as routers and switches to clear poisoned ARP entries.

Conclusion

ARP Redirect attacks exploit vulnerabilities in the ARP protocol to intercept and manipulate network traffic. By poisoning the ARP cache of victims, attackers can position themselves as intermediaries, capturing or altering sensitive data.

To protect against these attacks, organizations should implement preventive security measures such as static ARP entries, network monitoring, and encrypted communications. Additionally, response strategies like ARP cache inspections, network traffic analysis, and attacker blocking should be in place to detect and mitigate threats efficiently.

By maintaining continuous network monitoring and employing a proactive security approach, organizations can significantly reduce the risk of ARP-based attacks and ensure secure network communication.

ARP Spoofing: Network Security Threats and Defense Strategies