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Port Knocking!

Terminal - Port Knocking!
knock <host> 3000 4000 5000 && ssh -p <port> user@host && knock <host> 5000 4000 3000
2009-07-28 14:08:01
User: din7
Functions: ssh
Port Knocking!

Knock on ports to open a port to a service (ssh for example) and knock again to close the port. You have to install knockd.

See example config file below.


logfile = /var/log/knockd.log


sequence = 3000,4000,5000

seq_timeout = 5

command = /sbin/iptables -A INPUT -i eth0 -s %IP% -p tcp --dport 22 -j ACCEPT

tcpflags = syn


sequence = 5000,4000,3000

seq_timeout = 5

command = /sbin/iptables -D INPUT -i eth0 -s %IP% -p tcp --dport 22 -j ACCEPT

tcpflags = syn


There are 3 alternatives - vote for the best!

Terminal - Alternatives

Know a better way?

If you can do better, submit your command here.

What others think

extremely sweet. always. port knocking in da bomb diggity.

Comment by linuxrawkstar 322 weeks and 6 days ago


Comment by sameet 322 weeks and 5 days ago

Nice. Though I prefer ostiary (http://ingles.homeunix.net/software/ost/index.html) for things like that.

Comment by namelessjon 322 weeks and 5 days ago

That's awesome. It adds a security layer against brute forcers.

Comment by pyrho 322 weeks and 5 days ago

That's the correct link to Ostiary btw: http://ingles.homeunix.net/software/ost/ .

The one above included the ')'.

Comment by pyrho 322 weeks and 5 days ago

cursed brackets. Thanks for fixing that. :)

Ostiary also has a second advantage over port knocking as presented here. You can run it on an unused port (like the telnet port), and use over VPNs, which often block out the high ports often used for knocking.

Comment by namelessjon 322 weeks and 2 days ago

Whoa, what is this voodoo? That is way cooler than I'd imagine.

Comment by shurane 238 weeks and 4 days ago

Your point of view

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