If I am not mistaken dovecot has already limited concurrent accounts/ips. Furthermore I thought it would be obvious of course to utilize for this only unused resources and don't jeopardize a production environment.
Furthermore it is logical to assume that one abuse host is not dedicated to me. So it probably has 50? other connections for every one of mine. So if it would be common practice to dump abuse to /dev/zero, the abuse host would be the first to 'die'. -----Original Message----- From: Gerald Galster via dovecot [mailto:dovecot@dovecot.org] Sent: donderdag 11 april 2019 12:57 To: dovecot@dovecot.org Subject: Re: Mail account brute force / harassment Am 11.04.2019 um 12:43 schrieb Marc Roos via dovecot <dovecot@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 Maybe you want to look into a solution like 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@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 ^[^#] :-)
