How to Stop Bruit Force ssh Attempts?

Jonathan Franks daemon at taconic.net
Wed Apr 12 01:35:20 UTC 2006


On Mar 18, 2006, at 12:39 PM, Chris Maness wrote:

> In my auth log I see alot of bruit force attempts to login via  
> ssh.  Is there a way I can have the box automatically kill any tcp/ 
> ip connectivity to hosts that try and fail a given number of  
> times?  Is there a port or something that I can install to give  
> this kind of protection.  I'm still kind of a FreeBSD newbie.

If you are using PF, you can use source tracking to drop the  
offenders in to a table... perhaps after a certain number of attempts  
in a given time (say, 5 in a minute). Once you have the table you're  
in business... you can block based on it... and then set up a cron  
job to copy the table to disk every so often (perhaps once every two  
minutes). It works very well for me, YMMV.

If you don't want to block permanently, you could use cron to flush  
the table every so often too... I don't bother though.

-Jonathan


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