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Paolo Iannelli Picture

Paolo Iannelli

Big Daddy at Mega Labs

Location
Amsterdam Area, Netherlands
Industry
Information Technology and Services
Interests
C, Python, Big Data, Scalability, High Availability, Performance
Description
Expert Software Engineer with more than 12 years of experience.
Strong in critical thinking, problem solving and high performance architectures.
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SSH Port Knocking on Ubuntu

Posted on : 09-03-2011 | By : Paolo Iannelli | In : Security, System Administration

Tags: , ,

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My friend Ronny Roethof posted on his blog an interesting article about SSH Port Knocking. Before linking you to his article, I would like to briefly talk about this technology.

What is Port Knocking?

How many of you did ever open a door without even asking for who is behind it, recognizing the door knocking sequence of your friends?
Probably everyone of you.
Port Knocking in a Linux System works exactly the same.
In the setup Ronny discuss about SSH Port Knocking and how to secure SSH access from unauthorized people, simply leaving the default port 22 for SSH closed and opening it only after a sequence of TCP/IP packets on specific ports.

Cool! How do I do that ?

Supposing that before opening the port 22 we want to send a sequence of 1 syn packet to port 1234 and 1 syn packet to port 4321 (the entire sequence is fully customizable), we can follow Ronny’s instructions on his blog post and having it done in couple of minutes.