cache poisoning

Cache poisoning, often referred to in the context of DNS spoofing, involves corrupting the cache of a DNS resolver by inserting malicious or false DNS records. This leads to incorrect mappings of domain names to IP addresses, which can redirect users to fraudulent or malicious sites. Here’s a deeper look at cache poisoning:

How Cache Poisoning Works

1. DNS Resolution Process: When a user queries a domain name, the DNS resolver checks its cache for the corresponding IP address. If it's not found, the resolver queries external DNS servers.

2. Attack Execution:

   • Injection: The attacker sends a fake DNS response to the resolver before the legitimate response arrives. This response contains a malicious IP address associated with the queried domain.
   • Exploiting Vulnerabilities: Attackers may exploit weaknesses in the DNS protocol, such as predictable transaction IDs, to ensure their forged response is accepted.

3. Cache Update: If the resolver accepts the forged response, it caches the incorrect IP address, which can remain for the duration of the Time to Live (TTL) specified in the DNS records.

4. Subsequent Requests: Users attempting to access the affected domain will be directed to the attacker's IP address instead of the legitimate one.

Implications of Cache Poisoning

• Phishing and Fraud: Users may unknowingly visit malicious sites that mimic legitimate ones, leading to credential theft or malware infections.
• Data Interception: Sensitive information transmitted to the spoofed site can be captured by the attacker.
• Denial of Service: By redirecting traffic away from legitimate services, attackers can disrupt operations.

Prevention Strategies

1. DNSSEC (Domain Name System Security Extensions):

   • Digital Signatures: DNSSEC allows DNS responses to be signed, ensuring authenticity and integrity.
   • Validation: Resolvers can validate that the data they receive has not been tampered with.

2. Randomized Transaction IDs and Source Ports:

   • Increased Randomness: Using random transaction IDs and source ports for DNS queries makes it significantly harder for attackers to guess the correct parameters to inject a malicious response.

3. Response Rate Limiting:

   • Limiting Responses: Configuring DNS servers to limit the number of responses to the same query can help mitigate flooding attacks.

4. Regular Software Updates:

   • Patching Vulnerabilities: Keeping DNS server software updated ensures that known vulnerabilities are addressed.

5. Monitoring DNS Traffic:

   • Anomaly Detection: Regularly monitoring and analyzing DNS queries and responses can help detect unusual patterns indicative of cache poisoning.

6. Implementing Firewall and Access Control:

   • Restricting Access: Firewalls can help prevent unauthorized access to DNS servers and limit exposure to potential attackers.