Am 18.07.2017 um 22:15 schrieb mj: > 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?
i guess not, but typical bots arent using ssl, check it however fail2ban sometimes is to slow but as an alternative you may create a filter out of syslog to directly feed in iptables recent, here is an example with smtp https://sys4.de/de/blog/2012/12/28/botnets-mit-rsyslog-und-iptables-recent-modul-abwehren/ > > Thanks for the quick replies! > > MJ > > 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 >> Best Regards MfG Robert Schetterer -- [*] sys4 AG http://sys4.de, +49 (89) 30 90 46 64 Schleißheimer Straße 26/MG, 80333 München Sitz der Gesellschaft: München, Amtsgericht München: HRB 199263 Vorstand: Patrick Ben Koetter, Marc Schiffbauer Aufsichtsratsvorsitzender: Florian Kirstein
