Thousands of ssh probes
dc at dcoder.net
Sun Mar 7 20:58:36 UTC 2010
+++ Erik Norgaard [06/03/10 02:44 +0100]:
>On 05/03/10 13:54, John wrote:
>>My nightly security logs have thousands upon thousands of ssh probes
>>in them. One day, over 6500. This is enough that I can actually
>>"feel" it in my network performance. Other than changing ssh to
>>a non-standard port - is there a way to deal with these? Every
>>day, they originate from several different IP addresses, so I can't
>>just put in a static firewall rule. Is there a way to get ssh
>>to quit responding to a port or a way to generate a dynamic pf
>>rule in cases like this?
>This is a frequent question on the list, search the archives. Basically
>there are few things that you can do:
>1. limit the access to a range of IPs, for example, even if you travel a
>lot you go to al limited number of countries, why permit access from
>2. limit access to certain users, there is no need to allow games or
>root user to authenticate via ssh. Use AllowUsers or AllowGroups to
>restrict access to real users.
>3. limit the amount of concurrent non-authenticated connections, number
>of failed attempts and similar.
>4. prohibit password authentication.
>If the problem is that these attacks consume significant bandwidth then
>moving your service to a different port may be a good solution, but if
>your concern is security, then the above is more effective.
>Ph: +34.666334818/+34.915211157 http://www.locolomo.org
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has anybody suggested having sshd listen on a high port?
network engineer emeritus, verio/ntt
telluride, co & washington, dc
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