💬 Every DNS message, whether a query or a response, follows a...

Title: Every DNS message, whether a query or a response, follows a precisely defined binary format specified in RFC 1035. Understanding the fields inside a raw DNS packet is essential for understanding how attacks are constructed and why they work. The most important fields are as follows. The Transaction ID is a 16 bit random number generated by the client for each query. The server must echo this same ID in its response, and the client uses it to match responses to their corresponding queries. The...
Full Transcript: Every DNS message, whether a query or a response, follows a precisely defined binary format specified in RFC 1035. Understanding the fields inside a raw DNS packet is essential for understanding how attacks are constructed and why they work. The most important fields are as follows. The Transaction ID is a 16 bit random number generated by the client for each query. The server must echo this same ID in its response, and the client uses it to match responses to their corresponding queries. The QR flag indicates whether the message is a query (0) or a response (1). The RD flag (Recursion Desired) tells the server whether the client wants it to perform recursive lookups. The RA flag (Recursion Available) tells the client whether the server is capable of recursion. The ANCOUNT field indicates how many answer records are present in the response. From an attacker's perspective, the Transaction ID is the most critical field. Because DNS traditionally operates over UDP, there is no connection handshake to verify the source. Any machine on the network that sends a UDP packet with the correct Transaction ID and source port to the victim before the legitimate server responds can successfully poison the cache. This race condition is the fundamental vulnerability that makes DNS Cache Poisoning possible
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Every DNS message, whether a query or a response, follows a precisely defined binary format specified in RFC 1035. Understanding the fields inside a raw DNS packet is essential for understanding how attacks are constructed and why they work. The most important fields are as follows. The Transaction ID is a 16 bit random number generated by the client for each query. The server must echo this same ID in its response, and the client uses it to match responses to their corresponding queries. The...