Attacks on ssh port

[Willem Jan Withagen]

Peter Radcliffe wrote:

>Willem Jan Withagen <wjw at withagen.nl> probably said:
>  
>
>>I also have portsentry in a rather sensitive mode doing exactly the same 
>>thing.
>>Trigger one of  the "backdoor" ports, and you're out of my game.
>>    
>>
>
>The general problm with this type of reactive filtering is that if
>someone can spoof the source addresses effectively or cause a connection
>from a legitimate host you've just DoSed yourself...
>
>Personally I only allow ssh from known legitimate sources and block the
>rest so the "noise" is in a completely different list.
>  
>
I do too, on systems that are completly mine. But I had to "force" this 
customer to refrain from using
ftp/telnet/... with plain open passwords. And access to this box is 
required from verious remote locations with yet unknown IPs. So I have 
little chances there.

As far as I know, you need to go thru a lot of trouble to complete a 
spoofed full 3-way handshake just to get my maintenace IP-number blocked.
Next to the fact that there is a rule before the blocked list which lets 
me in anyways.... :)

--WjW