Re: under another kind of attack

Am 25.07.2017 um 16:54 schrieb mj:

Hi Olaf,

Since we implemented country blocking, everything seems nicely under control, with only 'normal levels' of knocking.

We first have impemented: http://blog.jeshurun.ca/technology/block-countries-ubuntu-iptables-xtables-g...

Then we did: https://github.com/firehol/blocklist-ipsets

simply geoip blocking may work at your site but it does not work for many other cases

And finale iptables rules like these:

...

iptables -A INPUT -p tcp --dport 143 -m geoip --src-cc CN,AG,MX,NI,MF,VE,CO,AR,RU,UA -j DROP iptables -A INPUT -p tcp --dport 143 -m geoip --src-cc MD,SD,SS,GA,CN,AZ,IN,ID,KZ,LA -j DROP iptables -A INPUT -p tcp --dport 143 -m geoip --src-cc MY,MN,SG,VN,TH,TW,HK,KR,KP,HT -j DROP iptables -A INPUT -p tcp --dport 143 -m geoip --src-cc CR,MZ -j DROP

iptables -A INPUT -p tcp --dport 993 -m geoip --src-cc CN,AG,MX,NI,MF,VE,CO,AR,RU,UA -j DROP iptables -A INPUT -p tcp --dport 993 -m geoip --src-cc MD,SD,SS,GA,CN,AZ,IN,ID,KZ,LA -j DROP iptables -A INPUT -p tcp --dport 993 -m geoip --src-cc MY,MN,SG,VN,TH,TW,HK,KR,KP,HT -j DROP iptables -A INPUT -p tcp --dport 993 -m geoip --src-cc CR,MZ -j DROP

iptables -A INPUT -p tcp --dport 465 -m geoip --src-cc CN,AG,MX,NI,MF,VE,CO,AR,RU,UA -j DROP iptables -A INPUT -p tcp --dport 465 -m geoip --src-cc MD,SD,SS,GA,CN,AZ,IN,ID,KZ,LA -j DROP iptables -A INPUT -p tcp --dport 465 -m geoip --src-cc MY,MN,SG,VN,TH,TW,HK,KR,KP,HT -j DROP iptables -A INPUT -p tcp --dport 465 -m geoip --src-cc CR,MZ -j DROP

I tried to combine the various dports in one single rule, but that didn't seem to work. Perhaps someone here knows how to combine --match "geoip" and "multiport" in one single rule?

Anyway: for us these combined measures did the tric.

Users in one of the imap-blocked countries will have to use ActiveSync (works over https), the webmail-interface, or launch the VPN first.

This works for us.

Only one thing on my wishlist: application specific passwords. I would very much appreciate a respond on that thread... (posted yesterday evening, with a pseudo-dovecot-config file...)

Hope the above helps you a bit, Olaf.

MJ

On 07/25/2017 04:37 PM, Olaf Hopp wrote:

...

Hi folks,

"somehow" similar to the thread "under some kind oof attack" started by "MJ":

I have dovecot shielded by fail2ban which works fine. But since a few days I see many many IPs per day knocking on my doors with wron password and/or users. But the rate at which they are knocking is very very low. So fail2ban will never catch them.

For example one IP:

Jul 25 14:03:17 irams1 dovecot: auth-worker(2212): pam(eurodisc,101.231.247.210,): unknown user Jul 25 15:16:36 irams1 dovecot: auth-worker(11047): pam(gergei,101.231.247.210,): pam_authenticate() failed: Authentication failure (password mismatch?) Jul 25 16:08:51 irams1 dovecot: auth-worker(3379): pam(icpe,101.231.247.210,): unknown user Jul 25 16:10:47 irams1 dovecot: auth-worker(4250): pam(endsulei,101.231.247.210,): unknown user

Note the timestamps. If I look the other way round (tries to one account) I'll get

Jul 25 01:30:48 irams1 dovecot: auth-worker(11276): pam(endsulei,60.166.12.117,<slp6mhhViI48pgx1>): unknown user Jul 25 01:31:26 irams1 dovecot: auth-worker(11276): pam(endsulei,222.243.211.200,): unknown user Jul 25 13:29:22 irams1 dovecot: auth-worker(4745): pam(endsulei,60.2.50.114,<4elhpCJVtcw8AjJy>): unknown user Jul 25 13:30:27 irams1 dovecot: auth-worker(4747): pam(endsulei,222.84.118.83,<kaE1qCJVn7neVHZT>): unknown user Jul 25 16:10:47 irams1 dovecot: auth-worker(4250): pam(endsulei,101.231.247.210,): unknown user Jul 25 16:11:45 irams1 dovecot: auth-worker(5933): pam(endsulei,206.214.0.120,<R5H56CRVdJfO1gB4>): unknown user

Also note the timestamps!

And I see many many distinct IPs per day (a few hundred) trying many many existing and non-existings accounts. As you see in the timestamps in my examples, this can not be handled by fail2ban without affecting regular users with typos. Is anybody observing something similar ? Anybody an idea against this ? Many of these observed IPs are chinese mobile IPs, if this matters. But we have also chinese students and researchers all abroad.

Regards, Olaf

Best Regards MfG Robert Schetterer

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