TNOK – NEXT GENERATION PORT SECURITY

Summary from the TLDR InfoSec newsletter

Tnok is a port security tool that employs time-based one-time passwords (TOTP) as dynamic port knock sequences. It encodes 6-digit 2FA codes into network packets sent to the target port: for UDP, the code is included in packet data, and for TCP, codes are encoded in TCP options (like MD5 and Mood) or distributed across multiple SYN packets via MSS values to avoid requiring root privileges. The system keeps protected ports closed until a valid TOTP code is received, after which it temporarily grants access without additional firewall configuration.