iptables in linux

Roger arelem at bigpond.com
Sat Nov 12 10:19:37 UTC 2011


I'm learning about iptables...
I find the same ip address sometimes 100 times or more and trying the
same user name.
After reading and applying much of the help in google I have tried and
failed to achieve a successful result.

for example: /var/log/btmp shows:
user ssh:notty   Thu Nov 10 17:10 - 17:10  (00:00)    hn.vtc.vn
some 30 times
user ssh:notty   Thu Nov 10 17:10 - 00:20 (1+07:10)   hn.vtc.vn 
3 times with varying duration.  
user ssh:notty   Thu Nov 10 13:14 - 17:07  (03:53)     58.250.71.43
25 times with varying duration.
and similar page after page.

Is there a way to limit:
-number of log in attempts to 2, 
-the duration of a log in attempt to 3 seconds or less
-the number of times a username can be tried, prefer it set at 2 and
then not again for 24 hours if it fails.

Also is there a way to DROP ip addresses after 2 attempts and not allow
that ip address for say 24 hours?

I did not find anything about this in the tutorials.
iptables does not seem difficult to grasp but I am completely stumped on
how to create tighter limits.

in part I have:
DROP  tcp  --  anywhere   anywhere  tcp dpt:ssh state NEW recent: UPDATE
seconds: 90 hit_count: 4 TTL-Match name: SSH1 side: source

And have tried seconds between 5 and 90 but find even login attempts of
2-5 minutes are not dropped.
hit_count set between 1 and 4 I still see 30+ attempts using the same
username attempt.

Help gratefully appreciated
thanks
Roger




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