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SMTP auth & DoS filter

Posted: Wed Dec 05, 2018 9:08 am
by rulezz
Hello!

It seems repetitive smtp auth failures do not trigger DoS filter. I see lot of messages in my zimbra.log

Code: Select all

Dec  4 12:34:17 mail postfix/smtpd[19169]: warning: unknown[49.73.158.65]: SASL LOGIN authentication failed: authentication failure
Dec  4 12:34:19 mail postfix/smtpd[19745]: warning: unknown[49.73.158.65]: SASL LOGIN authentication failed: authentication failure
Dec  4 12:34:23 mail postfix/smtpd[19169]: warning: unknown[49.73.158.65]: SASL LOGIN authentication failed: authentication failure
Dec  4 12:34:27 mail postfix/smtpd[19169]: warning: unknown[49.73.158.65]: SASL LOGIN authentication failed: authentication failure
Dec  4 12:34:30 mail postfix/smtpd[19745]: warning: unknown[49.73.158.65]: SASL LOGIN authentication failed: authentication failure
Dec  4 12:34:33 mail postfix/smtpd[19169]: warning: unknown[49.73.158.65]: SASL LOGIN authentication failed: authentication failure
Dec  4 12:34:37 mail postfix/smtpd[19745]: warning: unknown[49.73.158.65]: SASL LOGIN authentication failed: authentication failure
Dec  4 12:34:40 mail postfix/smtpd[19169]: warning: unknown[49.73.158.65]: SASL LOGIN authentication failed: authentication failure
Dec  4 12:34:41 mail postfix/smtpd[19745]: warning: unknown[49.73.158.65]: SASL LOGIN authentication failed: authentication failure
Dec  4 12:34:43 mail postfix/smtpd[19169]: warning: unknown[49.73.158.65]: SASL LOGIN authentication failed: authentication failure
Dec  4 12:34:45 mail postfix/smtpd[19745]: warning: unknown[49.73.158.65]: SASL LOGIN authentication failed: authentication failure


But IP 49.73.158.65 is not suspended. So there is possibility to brute force account password by SMTP auth. How can I prevent it?
Where is SASL log in zimbra? How can I figure out which account was used for auth?

Re: SMTP auth & DoS filter

Posted: Wed Dec 05, 2018 1:50 pm
by JDunphy
I haven't tested this but @lapsy added support in this script to display exactly for what you are asking provided you are running 8.8+.
https://github.com/JimDunphy/ZimbraScripts/blob/master/src/check_login.pl
The script will print a user and then all the ip addresses and type of failures (ie. pop/imap/web/smtp etc). I don't have 8.8+ so can't validate if it works for the smtp problem you are describing. My understanding the script can now handle this.Note: He also added the search feature so you can do a -s user and it will only do that email account on subsequent queries.
Ref:https://forums.zimbra.org/viewtopic.php?f=15&t=61294&hilit=check_login.pl

Re: SMTP auth & DoS filter

Posted: Wed Dec 05, 2018 2:20 pm
by fferraro87
JDunphy wrote:I haven't tested this but @lapsy added support in this script to display exactly for what you are asking provided you are running 8.8+.
https://github.com/JimDunphy/ZimbraScripts/blob/master/src/check_login.pl
The script will print a user and then all the ip addresses and type of failures (ie. pop/imap/web/smtp etc). I don't have 8.8+ so can't validate if it works for the smtp problem you are describing. My understanding the script can now handle this.Note: He also added the search feature so you can do a -s user and it will only do that email account on subsequent queries.
Ref:https://forums.zimbra.org/viewtopic.php?f=15&t=61294&hilit=check_login.pl

that script is awesome! thanks Jim

Re: SMTP auth & DoS filter

Posted: Wed Jan 23, 2019 2:04 pm
by xmana
JDunphy wrote:I haven't tested this but @lapsy added support in this script to display exactly for what you are asking provided you are running 8.8+.
https://github.com/JimDunphy/ZimbraScripts/blob/master/src/check_login.pl
The script will print a user and then all the ip addresses and type of failures (ie. pop/imap/web/smtp etc). I don't have 8.8+ so can't validate if it works for the smtp problem you are describing. My understanding the script can now handle this.Note: He also added the search feature so you can do a -s user and it will only do that email account on subsequent queries.
Ref:https://forums.zimbra.org/viewtopic.php?f=15&t=61294&hilit=check_login.pl


The script is wonderful! Thanks to the author!

Is there a ready-made solution for automatically blocking addresses from which brute force comes from?

By all protocols (POP3 / WEB / IMAP etc.)