DNS Spoofing (Cache Poisoning)

DNS spoofing, or cache poisoning, is a technique used to inject malicious DNS records into a resolver's cache. This allows attackers to redirect traffic from legitimate websites to fraudulent ones. Here’s a more detailed look at how it works, its implications, and ways to protect against it.

How DNS Spoofing Works

1. DNS Query Process: When a user requests a domain name, their DNS resolver queries various DNS servers to find the corresponding IP address.

2. Malicious Injection: An attacker exploits vulnerabilities in the DNS resolver, often by sending a forged DNS response that appears to come from a legitimate DNS server. This response contains incorrect IP address information.

3. Cache Update: The resolver, believing the response to be valid, updates its cache with the false information.

4. Traffic Redirection: Subsequent requests for the poisoned domain will be directed to the attacker’s specified IP address instead of the legitimate one, potentially leading to phishing sites or malicious content.

Implications

• Phishing Attacks: Users may be redirected to fake websites that resemble legitimate ones, leading to credential theft or malware installation.
• Data Theft: Attackers can harvest sensitive information by directing users to malicious sites.
• Loss of Trust: Organizations affected by DNS spoofing may suffer reputational damage.

Prevention Strategies

1. DNSSEC (Domain Name System Security Extensions): This adds a layer of security by digitally signing DNS data, ensuring that responses are authentic and unaltered.

2. Use of Randomized Source Ports: Randomizing the source port of DNS queries makes it harder for attackers to predict and spoof responses.

3. Response Rate Limiting: Limiting the number of responses a DNS server will send to prevent overwhelming the server with queries.

4. Regularly Updating Software: Keeping DNS server software and security patches up to date helps mitigate known vulnerabilities.

5. Monitoring and Logging: Actively monitoring DNS queries and responses for unusual patterns can help detect and respond to spoofing attempts.

6. Implementing Firewall Rules: Use firewalls to restrict access to DNS servers and limit external queries.