Knock: A Linux kernel patch for NAT-compatible, stealthy port knocking

Linux

A Linux kernel patch that “implements a new NAT-compatible, TCP option for stealthy port knocking with a few new twists for improved security” has been released.

Port knocking is a security implementation that’s designed to reduce the visibility of TCP servers on the network. A good port knock tool renders TCP servers stealthy, making them invisible to port scanners.

The point of a port knock tool is to make TCP servers respond to TCP SYN request only after a pre-defined sequence of packets have been sent and received. It’s like having a club house whose doors open only after a set number and sequence of knocks. There have been tools like in the past, but as far as I know, all have been in user space. Knock is thus likely the first port knock tool for Linux in kernel space.

Related Post:  Bigger fines for Google, Microsoft in proposed EU data privacy laws

From the release announcement:

  • Knocking is done in the Linux kernel. Applications can activate Knock with a single additional setsockopt call (in both client and server). Thus, once Linux has been patched, deployment will be much simpler compared to other implementations. Also, as Knock operates in the Kernel, timing attacks should be much harder to do.
  • Our Knock optionally does not merely enable opening the connection, but also can be used to protect the first N bytes of the TCP payload. Thus, given a sane protocol being run above TCP (one begins with a key exchange), an active attacker cannot simply take over the TCP connection after the handshake without also being locked into sending the same TCP payload. Thus, if the client begins by sending his public key and then continues to send data that must be authenticated with that key, even an active man-in-the-middle adversary cannot hijack the connection.

Knock is the work of Julian Kirsch, Maurice Leclaire and Christian Grothoff. The complete release announcement, associated documentations, as well as the code, are available here. The patch has been submitted to the Linux Kernel Mailing List (LKML), the kernel networking mailing list and subsystem maintainer. Could be coming to a Linux kernel next, if it passes muster.

Related Post:  Is systemd as bad as boycott systemd is trying to make it?

Share:

Share on facebook
Facebook
Share on twitter
Twitter
Share on pinterest
Pinterest
Share on linkedin
LinkedIn

Hola! Did you notice that LinuxBSDos.com no longer run network ads?  Yep, no more ads from the usual suspects that track and annoy you across the Internet. But since I still need to pay to keep the site running, feel free to make a small donation by PayPal or your favorite cryptocurrency.

  • Bitcoin
  • Ethereum
  • Xrp
  • Bitcoin cash
  • Bitcoin sv
  • Litecoin
  • Binance coin
  • Cardano
  • Ethereum classic
Scan to Donate Bitcoin to bc1qzvlte2m224zkayhdc7fdfjkp2rsgt0l5a496ua

Donate Bitcoin to this address

Scan the QR code or copy the address below into your wallet to send some Bitcoin

Scan to Donate Ethereum to 0x0F4362DFF77F3Ba0Dc637F5f3Eba35D09a2fA60C

Donate Ethereum to this address

Scan the QR code or copy the address below into your wallet to send some Ethereum

Scan to Donate Xrp to r4ggjvL36njsMCYTkJ3S7cTHscPsMsSGQv

Donate Xrp to this address

Scan the QR code or copy the address below into your wallet to send some Xrp

Scan to Donate Bitcoin cash to qrs0dedzp9t55af3nfwypydghp29r0xguy9s20fz2k

Donate Bitcoin cash to this address

Scan the QR code or copy the address below into your wallet to send some Bitcoin cash

Scan to Donate Bitcoin sv to 15K9TLyVDBtLuG9cYvXCX9SSkq9C9oUKHK

Donate Bitcoin sv to this address

Scan the QR code or copy the address below into your wallet to send some Bitcoin sv

Scan to Donate Litecoin to LetJ9QQMb7u2LMZ9Tu6rtHwcBcQFW98fbG

Donate Litecoin to this address

Scan the QR code or copy the address below into your wallet to send some Litecoin

Scan to Donate Binance coin to bnb1ga8trq08ssqepd90v6225nzfgy448pu5pw8gxp

Donate Binance coin to this address

Scan the QR code or copy the address below into your wallet to send some Binance coin

Scan to Donate Cardano to addr1qx2354yw49etstfljpdhwja3ajjlt487lg95vu9ngy2q6vu4rf2ga2tjhqknlyzmwa9mrm997h20a7stgectxsg5p5esq5l7d9

Donate Cardano to this address

Scan the QR code or copy the address below into your wallet to send some Cardano

Scan to Donate Ethereum classic to 0xcD6CC972a2297FcafACDcfE042C55C69516a9264

Donate Ethereum classic to this address

Scan the QR code or copy the address below into your wallet to send some Ethereum classic

Subscribe for updates. Trust me, no spam!

Sponsored links

1. Attend Algorithm Conference, a top AI and ML event.
2. Reasons to use control panel for your server.
3. DHgate Computers Electronics, Cell Phones & more.

Upcoming events

Leave a Reply

Your email address will not be published. Required fields are marked *

Get the latest

On social media
Via my newsletter

Partner links

1. Attend Algorithm Conference, a top AI and ML event for 2021.
2. Reasons to use control panel for your server.
3. DHgate Computers Electronics, Cell Phones & more.
Hacking, pentesting distributions

Linux Distributions for Hacking

Experts use these Linux distributions for hacking, digital forensics, and pentesting.

Categories
Archives

The authors of these books are confirmed to speak during

Algorithm Conference

T-minus AI

Author was the first chairperson of AI for the U.S. Air Force.

The case for killer robots

Author is the Director of the Center for Natural and Artificial Intelligence.

Why greatness cannot be planned

Author works on AI safety as a Senior Research Scientist at Uber AI Labs.