Mail account brute force / harassment

[Gerald Galster]

> Am 11.04.2019 um 12:43 schrieb Marc Roos via dovecot <dovecot at dovecot.org>:
> 
> Please do not assume anything other than what is written, it is a 
> hypothetical situation
> 
> 
> A. With the fail2ban solution
>   - you 'solve' that the current ip is not able to access you
>   - it will continue bothering other servers and admins
>   - you get the next abuse host to give a try.
> 
> B. With 500GB dump
> - the owner of the attacking server (probably hacked) will notice it 
> will be forced to take action.
> 
> 
> If abuse clouds are smart (most are) they would notice that attacking my 
> servers, will result in the loss of abuse nodes, hence they will not 
> bother me anymore. 
> 
> If every one would apply strategy B, the abuse problem would get less. 
> Don't you agree??

I disagree. If 100 servers "hack" your imap account and fetch 500GB then
most likely your server is unreachable. If this is done over many servers
then your rack switches become the bottleneck and uninvolved servers are
affected too.

Your solution may work if traffic is expensive and limited but we're heading
in the other direction: you can rent a server for 50 bucks with 1gbit bandwidth
and unmetered traffic e.g. at hetzner.de <http://hetzner.de/>

Maybe you want to look into a solution like weakforced:

https://github.com/PowerDNS/weakforced <https://github.com/PowerDNS/weakforced>
Wforce is a project by Dovecot, PowerDNS and Open-Xchange

Best regards
Gerald



> 
> 
> 
> 
> 
> 
> -----Original Message-----
> From: Odhiambo Washington  
> Sent: donderdag 11 april 2019 12:28
> To: Marc Roos
> Cc: dovecot
> Subject: Re: Mail account brute force / harassment
> 
> 
> 
> On Thu, 11 Apr 2019 at 13:24, Marc Roos via dovecot 
> <dovecot at dovecot.org> wrote:
> 
> 
> 
> 
> 	Say for instance you have some one trying to constantly access an 
> 	account
> 	
> 	
> 	Has any of you made something creative like this:
> 	
> 	* configure that account to allow to login with any password
> 	* link that account to something like /dev/zero that generates 
> infinite 
> 	amount of messages
> 	  (maybe send an archive of virusses?)
> 	* transferring TB's of data to this harassing client.
> 	
> 	I think it would be interesting to be able to do such a thing.
> 	
> 	
> 
> 
> Instead of being evil, just use fail2ban to address this problem :-)  
> 
> -- 
> 
> Best regards,
> Odhiambo WASHINGTON,
> Nairobi,KE
> +254 7 3200 0004/+254 7 2274 3223
> "Oh, the cruft.", grep ^[^#] :-)
> 
> 

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