DNS Cache Poisoning vs DNSSEC: Race the Spoofed Response

What DNS Cache Poisoning Is

DNS cache poisoning is an attack where malicious actors inject false data into the Domain Name System (DNS) cache of a recursive resolver. This can redirect users to fraudulent websites or block access to legitimate ones, compromising both security and privacy.

The attack works by sending forged DNS responses with a matching query ID (QID), which trick the resolver into updating its cache with incorrect information before the legitimate response arrives.

Why It Happens

DNS cache poisoning exploits the nature of recursive resolvers, which store and reuse DNS responses to speed up future queries. If an attacker can flood a resolver with a forged response before the real one is received, they can overwrite the legitimate data in the resolver’s cache.

This attack is particularly dangerous because it can be executed off-path, meaning the attacker does not need direct access to the client or the authoritative server.

DNSSEC: A Solution

DNSSEC (Domain Name System Security Extensions) introduces a layer of cryptographic security to DNS transactions. It ensures that each response is verified against a chain of trust from the root zone down to the authoritative server.

By verifying responses, DNSSEC prevents forged answers from being cached and thus mitigates cache poisoning attacks.

How DNSSEC Works

DNSSEC uses digital signatures to authenticate each DNS record. When a resolver receives a response, it checks the signature against a public key in its trust anchor database. If the signature is valid, the response is considered genuine and cached; otherwise, it’s discarded.

This process ensures that only legitimate responses are stored in the cache, thereby protecting users from being redirected to malicious sites.

Frequently asked questions

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