Re: SSH scans vs connection ratelimiting

Scot Hetzel wrote:

However, there apparently are SSH bruteforcers that simply use one
connection to perform a brute-force attack:

Aug 18 00:00:01 aberdeen sshd[87989]: Invalid user serwis from 83.19.113.122
Aug 18 00:00:03 aberdeen sshd[88010]: Invalid user serwis from 83.19.113.122
Aug 18 00:00:05 aberdeen sshd[88012]: Invalid user serwis from 83.19.113.122
Aug 18 00:00:10 aberdeen sshd[88014]: Invalid user serwis from 83.19.113.122
Aug 18 00:00:13 aberdeen sshd[88019]: Invalid user serwis from 83.19.113.122
Aug 18 00:00:14 aberdeen sshd[88021]: Invalid user serwis from 83.19.113.122

It looks as though you need to lower 'MaxAuthTries' in your
sshd_config file, as the default is set to allow six authentication
attempts per connection.

I had already lowered this value to '3', which apparantly does not matter at all. I even forgot that I did, which says enough ;)

Makes me wonder even more what's happening; even with 3 auth sessions per connection, that would mean only 9 attempts per minute should be possible. I'm seeing >100 attempts per minute, though.

--
Pieter


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