Performance Tuning & Kernel Parameters (Sysctl)

Stop TCP timestamps from leaking your server uptime

🧩 The Challenge

You finally get the app stack stable and then security comes knocking because your TCP timestamps are giving away exactly how long the box has been up. It is a massive headache to explain that it’s just a kernel default and not some gaping hole in your firewall.

💡 The Fix

Flip a single sysctl bit to disable those timestamps and stop feeding information to anyone running a basic Nmap scan against your infrastructure. It won’t break your connection tracking, but it keeps the snoops guessing about your maintenance schedule.

sysctl -w net.ipv4.tcp_timestamps=0

⚙️ Why It Works

Setting this to zero stops the kernel from appending a timestamp to every packet, which effectively hides the system uptime from remote TCP fingerprinting tools. Don’t forget to drop that setting into a file in /etc/sysctl.d/ if you want it to survive a reboot.

🚀 Pro-Tip: Add the setting to a permanent file like 99-security.conf so it actually sticks after a bounce.

Linux Tips & Tricks | © ngelinux.com | 7/22/2026