TCP SYN Floods & SYN Cookies
The classic TCP 3-Way Handshake has an inherent asymmetry that attackers exploit for denial-of-service.
⚡ The Half-Open Vulnerability
Every incoming SYN allocates a socket structure in the kernel's SYN queue. If ACKs never arrive, the queue fills and all new connections drop.
🛡️ The Cryptographic Fix: SYN Cookies
By setting:
ISN = Hash(s_ip, d_ip, s_port, d_port, counter) + MSS index
the server remains completely stateless until the client sends the final ACK!
Explore the space-time protocol ladder on Binary Dose.
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