On Tuesday 18 July 2017 22:15:24 mj wrote: > Hi, > > Thanks for the quick follow-ups! Much appreciated. After posting this, I > immediately started working on fail2ban. And between my initial posting > and now, fail2ban already blocked 114 IPs. > > I have fail2ban with maxretry=1 and bantime=1800 > > However, it seems almost all IPs are different, and I don't think I can > keep the above settings permanently. > > Robert, your iptables suggestions are _very_ interesting! However, will > they also work on imaps/993, because of the ssl? > > Thanks for the quick replies! > > MJ
Why not? You can however let them retry 2-3 times , we all made mistakes :) If there is a real user in that ban list you will help him to found and remove the malware in his network. > > On 07/18/2017 09:52 PM, Robert Schetterer wrote: > > Am 18.07.2017 um 21:44 schrieb mj: > >> Hi all, > >> > >> It seems we are under some kind of password guessing attack: > >>> Jul 18 21:33:33 auth: Info: > >>> ldap(username1,103.6.223.61,<W7wLl5xUfABnBt89>): invalid credentials > >>> (given password: 1q2w3e4r5t) > >>> Jul 18 21:34:16 auth: Info: > >>> ldap(username1,221.4.61.180,<89WnmZxUrADdBD20>): invalid credentials > >>> (given password: 1q2w3e4r5t) > >>> Jul 18 21:36:13 auth: Info: > >>> ldap(username2,117.243.180.225,<ESWBoJxUdQB187Th>): invalid > >>> credentials (given password: 1q2w3e4r) > >>> Jul 18 21:36:50 auth: Info: > >>> ldap(username2,58.59.103.230,<j7fQopxUNgA6O2fm>): invalid credentials > >>> (given password: 1q2w3e4r) > >>> Jul 18 21:36:56 auth: Info: > >>> ldap(username4,58.215.13.154,<gtY5o5xUlQA61w2a>): invalid credentials > >>> (given password: 1q2w3e4r5t) > >>> Jul 18 21:37:18 auth: Info: > >>> ldap(username3,220.175.154.205,<lFxppJxUFADcr5rN>): invalid > >>> credentials (given password: 1q2w3e4r) > >>> Jul 18 21:37:25 auth: Info: > >>> ldap(username5,14.142.29.142,<40zopJxUSgAOjh2O>): invalid credentials > >>> (given password: 1q2w3e4r) > >>> Jul 18 21:37:27 auth: Info: > >>> ldap(username4,119.1.98.121,<JDQOpZxUCwB3AWJ5>): invalid credentials > >>> (given password: 1q2w3e4r5t) > >>> Jul 18 21:37:54 auth: Info: > >>> ldap(username3,218.76.156.11,<OMqtppxUMADaTJwL>): invalid credentials > >>> (given password: 1q2w3e4r) > >> > >> Different IPs, different usernames, but all (almost) the same password. > >> > >> Any idea what we can do about this?? > >> > >> Any advice you could give us would be very much appreciated. > >> > >> MJ > > > > perhaps this > > > > https://wiki.dovecot.org/HowTo/Fail2Ban > > > > > > or you may adapt this > > > > https://sys4.de/de/blog/2015/11/07/abwehr-des-botnets-pushdo-cutwail-ehlo-> > > > ylmf-pc-mit-iptables-string-recent-smtp/ > > > > https://sys4.de/de/blog/2014/03/27/fighting-smtp-auth-brute-force-attacks/ > > > > to pop3(s)/imap(s) and your needs > > > > > > > > > > Best Regards > > MfG Robert Schetterer
