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Gary Stainburn

2019-Apr-19 12:30 UTC

[CentOS] faI2ban detecting and banning but nothing happens

I've followed one of the pages on line specifically for installing fail2ban
on
Centos 7 and all looks fine.

I've added a fail regex to /etc/fail2ban/filter.d/exim.conf as suggested on 
another page:

       \[<HOST>\]: 535 Incorrect authentication data

which appears to be successfully matchnig lines in /var/log/exim/mail.log such 
as

2019-04-19 13:06:10 dovecot_plain authenticator failed for ([185.222.209.71]) 
[185.222.209.71]: 535 Incorrect authentication data

/var/log/fail2ban.log, and the generarted emails all say that the regex is 
working and the IP addresses are getting banned.

2019-04-19 13:06:32,461 fail2ban.filter         [21954]: INFO    [dovecot] 
Found 45.227.253.99
2019-04-19 13:06:32,607 fail2ban.actions        [21954]: NOTICE  [dovecot] Ban 
45.227.253.99
2019-04-19 13:06:32,954 fail2ban.filter         [21954]: INFO    [dovecot] 
Found 45.227.253.99
2019-04-19 13:06:36,664 fail2ban.filter         [21954]: INFO    [dovecot] 
Found 185.222.209.71
2019-04-19 13:07:16,973 fail2ban.actions        [21954]: NOTICE  [dovecot] 
Unban 185.211.245.198
2019-04-19 13:07:42,108 fail2ban.actions        [21954]: NOTICE  [dovecot] 
Unban 185.234.217.221
2019-04-19 13:08:06,475 fail2ban.filter         [21954]: INFO    [dovecot] 
Found 141.98.80.32
2019-04-19 13:08:11,299 fail2ban.filter         [21954]: INFO    [dovecot] 
Found 185.234.217.162
2019-04-19 13:08:12,249 fail2ban.actions        [21954]: NOTICE  [dovecot] Ban 
185.234.217.162
2019-04-19 13:08:16,803 fail2ban.filter         [21954]: INFO    [dovecot] 
Found 141.98.80.32
2019-04-19 13:08:22,092 fail2ban.filter         [21954]: INFO    [dovecot] 
Found 185.234.217.221
2019-04-19 13:09:18,178 fail2ban.filter         [21954]: INFO    [dovecot] 
Found 185.211.245.198
2019-04-19 13:09:30,522 fail2ban.filter         [21954]: INFO    [dovecot] 
Found 185.211.245.198
2019-04-19 13:09:30,752 fail2ban.actions        [21954]: NOTICE  [dovecot] Ban 
185.211.245.198
2019-04-19 13:10:48,248 fail2ban.filter         [21954]: INFO    [dovecot] 
Found 185.211.245.198



However, once an IP address is banned, it continues to appear 
in /var/log/exim/main.log which would imply that the ban action is not 
working.

(Also, I don't understand why it's matching against dovecont ewhen the
regex
is in exim.conf)

I've found lots of pages relating to regex errors which this obviously
isn't
but I can't seem to find pages about why the ban doesn't work. Does
anyone
have any ideas?

Pete Biggs

2019-Apr-19 14:19 UTC

head link

[CentOS] faI2ban detecting and banning but nothing happens

> I've added a fail regex to /etc/fail2ban/filter.d/exim.conf as
suggested on
> another page:
The standard exim.conf already has a 535 filter. Was that not working
for you?

> 
>        \[<HOST>\]: 535 Incorrect authentication data
> 
> which appears to be successfully matchnig lines in /var/log/exim/mail.log
such
> as
> 
> 2019-04-19 13:06:10 dovecot_plain authenticator failed for
([185.222.209.71])
> [185.222.209.71]: 535 Incorrect authentication data
Just to check - you are authenticating against dovecot for SMTP within
exim (and it's not that dovecot authentication is getting mixed up with
the exim logs)?
> 
> /var/log/fail2ban.log, and the generarted emails all say that the regex is 
> working and the IP addresses are getting banned.
> 
> 2019-04-19 13:06:32,461 fail2ban.filter         [21954]: INFO    [dovecot] 
> Found 45.227.253.99
> 2019-04-19 13:06:32,607 fail2ban.actions        [21954]: NOTICE  [dovecot]
Ban
> 45.227.253.99
> 2019-04-19 13:06:32,954 fail2ban.filter         [21954]: INFO    [dovecot] 
> Found 45.227.253.99
> 2019-04-19 13:06:36,664 fail2ban.filter         [21954]: INFO    [dovecot] 
> Found 185.222.209.71
> 2019-04-19 13:07:16,973 fail2ban.actions        [21954]: NOTICE  [dovecot] 
> Unban 185.211.245.198
> 2019-04-19 13:07:42,108 fail2ban.actions        [21954]: NOTICE  [dovecot] 
> Unban 185.234.217.221
> 2019-04-19 13:08:06,475 fail2ban.filter         [21954]: INFO    [dovecot] 
> Found 141.98.80.32
> 2019-04-19 13:08:11,299 fail2ban.filter         [21954]: INFO    [dovecot] 
> Found 185.234.217.162
> 2019-04-19 13:08:12,249 fail2ban.actions        [21954]: NOTICE  [dovecot]
Ban
> 185.234.217.162
> 2019-04-19 13:08:16,803 fail2ban.filter         [21954]: INFO    [dovecot] 
> Found 141.98.80.32
> 2019-04-19 13:08:22,092 fail2ban.filter         [21954]: INFO    [dovecot] 
> Found 185.234.217.221
> 2019-04-19 13:09:18,178 fail2ban.filter         [21954]: INFO    [dovecot] 
> Found 185.211.245.198
> 2019-04-19 13:09:30,522 fail2ban.filter         [21954]: INFO    [dovecot] 
> Found 185.211.245.198
> 2019-04-19 13:09:30,752 fail2ban.actions        [21954]: NOTICE  [dovecot]
Ban
> 185.211.245.198
> 2019-04-19 13:10:48,248 fail2ban.filter         [21954]: INFO    [dovecot] 
> Found 185.211.245.198
> It would be much, much easier to read if you didn't wrap the log lines
- I've unwrapped them for you:

2019-04-19 13:06:32,461 fail2ban.filter         [21954]: INFO    [dovecot] Found
45.227.253.99
2019-04-19 13:06:32,607 fail2ban.actions        [21954]: NOTICE  [dovecot] Ban
45.227.253.99
2019-04-19 13:06:32,954 fail2ban.filter         [21954]: INFO    [dovecot] Found
45.227.253.99
2019-04-19 13:06:36,664 fail2ban.filter         [21954]: INFO    [dovecot] Found
185.222.209.71
2019-04-19 13:07:16,973 fail2ban.actions        [21954]: NOTICE  [dovecot] Unban
185.211.245.198
2019-04-19 13:07:42,108 fail2ban.actions        [21954]: NOTICE  [dovecot] Unban
185.234.217.221
2019-04-19 13:08:06,475 fail2ban.filter         [21954]: INFO    [dovecot] Found
141.98.80.32
2019-04-19 13:08:11,299 fail2ban.filter         [21954]: INFO    [dovecot] Found
185.234.217.162
2019-04-19 13:08:12,249 fail2ban.actions        [21954]: NOTICE  [dovecot] Ban
185.234.217.162
2019-04-19 13:08:16,803 fail2ban.filter         [21954]: INFO    [dovecot] Found
141.98.80.32
2019-04-19 13:08:22,092 fail2ban.filter         [21954]: INFO    [dovecot] Found
185.234.217.221
2019-04-19 13:09:18,178 fail2ban.filter         [21954]: INFO    [dovecot] Found
185.211.245.198
2019-04-19 13:09:30,522 fail2ban.filter         [21954]: INFO    [dovecot] Found
185.211.245.198
2019-04-19 13:09:30,752 fail2ban.actions        [21954]: NOTICE  [dovecot] Ban
185.211.245.198
2019-04-19 13:10:48,248 fail2ban.filter         [21954]: INFO    [dovecot] Found
185.211.245.198
> 
> 
> However, once an IP address is banned, it continues to appear 
> in /var/log/exim/main.log which would imply that the ban action is not 
> working.
Only for one more attempt - I presume your ban action is to modify the
firewall, but the firewall doesn't stop established connections, so as
long as the remote host has an open TCP connection it can continue to
attempt to login. If your authenticator drops the connection after 3
attempts and Fail2Ban blocks after 2 failed attempts you will see what
you've got.
> 
> (Also, I don't understand why it's matching against dovecont ewhen
the regex
> is in exim.conf)
Because the log line says dovecot - the actual name of the .conf file
is irrelevant and nowhere in the filter config files does it mention
[exim] explicitly (or any other section). The section is determined
from the log line using the filters.

P.

Gary Stainburn

2019-Apr-19 14:35 UTC

head link

[CentOS] faI2ban detecting and banning but nothing happens

On Friday 19 April 2019 15:19:26 Pete Biggs wrote:> > I've added a fail regex to /etc/fail2ban/filter.d/exim.conf as
suggested
> > on another page:
>
> The standard exim.conf already has a 535 filter. Was that not working
> for you?
I was following the instructions as shown on the page.  I did find after 
sending my post that there was already a regex in the standard file, so 
should be able to remove the one I added. However, the regex part doesn't 
seem to be the problem as the actions are being correctly triggered.
> >        \[<HOST>\]: 535 Incorrect authentication data
> >
> > which appears to be successfully matchnig lines in
/var/log/exim/mail.log
> > such as
> >
> > 2019-04-19 13:06:10 dovecot_plain authenticator failed for
> > ([185.222.209.71]) [185.222.209.71]: 535 Incorrect authentication data
>
> Just to check - you are authenticating against dovecot for SMTP within
> exim (and it's not that dovecot authentication is getting mixed up with
> the exim logs)?
This is correct.  I am using Dovecot to authenticate the SMTP users.  The 
errors are being logged in /var/log/exim/main.log and not 
in /var/log/dovecot.log or /var/log/maillog
>
> > /var/log/fail2ban.log, and the generarted emails all say that the
regex
> > is working and the IP addresses are getting banned.
> >
> > 2019-04-19 13:06:32,461 fail2ban.filter         [21954]: INFO   
> > [dovecot] Found 45.227.253.99
> > 2019-04-19 13:06:32,607 fail2ban.actions        [21954]: NOTICE 
> > [dovecot] Ban 45.227.253.99
> > 2019-04-19 13:06:32,954 fail2ban.filter         [21954]: INFO   
> > [dovecot] Found 45.227.253.99
> > 2019-04-19 13:06:36,664 fail2ban.filter         [21954]: INFO   
> > [dovecot] Found 185.222.209.71
> > 2019-04-19 13:07:16,973 fail2ban.actions        [21954]: NOTICE 
> > [dovecot] Unban 185.211.245.198
> > 2019-04-19 13:07:42,108 fail2ban.actions        [21954]: NOTICE 
> > [dovecot] Unban 185.234.217.221
> > 2019-04-19 13:08:06,475 fail2ban.filter         [21954]: INFO   
> > [dovecot] Found 141.98.80.32
> > 2019-04-19 13:08:11,299 fail2ban.filter         [21954]: INFO   
> > [dovecot] Found 185.234.217.162
> > 2019-04-19 13:08:12,249 fail2ban.actions        [21954]: NOTICE 
> > [dovecot] Ban 185.234.217.162
> > 2019-04-19 13:08:16,803 fail2ban.filter         [21954]: INFO   
> > [dovecot] Found 141.98.80.32
> > 2019-04-19 13:08:22,092 fail2ban.filter         [21954]: INFO   
> > [dovecot] Found 185.234.217.221
> > 2019-04-19 13:09:18,178 fail2ban.filter         [21954]: INFO   
> > [dovecot] Found 185.211.245.198
> > 2019-04-19 13:09:30,522 fail2ban.filter         [21954]: INFO   
> > [dovecot] Found 185.211.245.198
> > 2019-04-19 13:09:30,752 fail2ban.actions        [21954]: NOTICE 
> > [dovecot] Ban 185.211.245.198
> > 2019-04-19 13:10:48,248 fail2ban.filter         [21954]: INFO   
> > [dovecot] Found 185.211.245.198
>
> It would be much, much easier to read if you didn't wrap the log lines
> - I've unwrapped them for you:(I didn't wrap them, my mail client did. Sorry)
>
> 2019-04-19 13:06:32,461 fail2ban.filter         [21954]: INFO    [dovecot]
> Found 45.227.253.99 2019-04-19 13:06:32,607 fail2ban.actions       
> [21954]: NOTICE  [dovecot] Ban 45.227.253.99 2019-04-19 13:06:32,954
> fail2ban.filter         [21954]: INFO    [dovecot] Found 45.227.253.99
> 2019-04-19 13:06:36,664 fail2ban.filter         [21954]: INFO    [dovecot]
> Found 185.222.209.71 2019-04-19 13:07:16,973 fail2ban.actions       
> [21954]: NOTICE  [dovecot] Unban 185.211.245.198 2019-04-19 13:07:42,108
> fail2ban.actions        [21954]: NOTICE  [dovecot] Unban 185.234.217.221
> 2019-04-19 13:08:06,475 fail2ban.filter         [21954]: INFO    [dovecot]
> Found 141.98.80.32 2019-04-19 13:08:11,299 fail2ban.filter         [21954]:
> INFO    [dovecot] Found 185.234.217.162 2019-04-19 13:08:12,249
> fail2ban.actions        [21954]: NOTICE  [dovecot] Ban 185.234.217.162
> 2019-04-19 13:08:16,803 fail2ban.filter         [21954]: INFO    [dovecot]
> Found 141.98.80.32 2019-04-19 13:08:22,092 fail2ban.filter         [21954]:
> INFO    [dovecot] Found 185.234.217.221 2019-04-19 13:09:18,178
> fail2ban.filter         [21954]: INFO    [dovecot] Found 185.211.245.198
> 2019-04-19 13:09:30,522 fail2ban.filter         [21954]: INFO    [dovecot]
> Found 185.211.245.198 2019-04-19 13:09:30,752 fail2ban.actions       
> [21954]: NOTICE  [dovecot] Ban 185.211.245.198 2019-04-19 13:10:48,248
> fail2ban.filter         [21954]: INFO    [dovecot] Found 185.211.245.198
>
> > However, once an IP address is banned, it continues to appear
> > in /var/log/exim/main.log which would imply that the ban action is not
> > working.
>
> Only for one more attempt - I presume your ban action is to modify the
> firewall, but the firewall doesn't stop established connections, so as
> long as the remote host has an open TCP connection it can continue to
> attempt to login. If your authenticator drops the connection after 3
> attempts and Fail2Ban blocks after 2 failed attempts you will see what
> you've got.
The event that triggers the ban does complete as normal, which is what I would 
expect as the ban is triggered by the log entry which is *after* the failed 
attempt.

However, after the /var/log/fail2ban.log showed the IP as banned, I continue 
to see entries in /var/log/exim/main.log
>
> > (Also, I don't understand why it's matching against dovecont ewhen
the> > regex is in exim.conf)
>
> Because the log line says dovecot - the actual name of the .conf file
> is irrelevant and nowhere in the filter config files does it mention
> [exim] explicitly (or any other section). The section is determined
> from the log line using the filters.
I did wonder that, but had initially assumed that the it took it from the 
module / target.

Kenneth Porter

2019-Apr-19 15:15 UTC

head link

[CentOS] faI2ban detecting and banning but nothing happens

On 4/19/2019 5:30 AM, Gary Stainburn wrote:> I've followed one of the pages on line specifically for installing
fail2ban on
> Centos 7 and all looks fine.
Which page? It would help to see what they advised.

Gary Stainburn

2019-Apr-26 10:50 UTC

head link

[CentOS] faI2ban detecting and banning but nothing happens

On Friday 19 April 2019 16:15:32 Kenneth Porter wrote:> On 4/19/2019 5:30 AM, Gary Stainburn wrote:
> > I've followed one of the pages on line specifically for installing
fail2ban on
> > Centos 7 and all looks fine.
> 
> Which page? It would help to see what they advised.
> On Friday 19 April 2019 16:15:32 Kenneth Porter wrote:
> On 4/19/2019 5:30 AM, Gary Stainburn wrote:
> > I've followed one of the pages on line specifically for installing
> > fail2ban on Centos 7 and all looks fine.
>
> Which page? It would help to see what they advised.
I think I worked from two pages. One I believe was 

https://www.howtoforge.com/tutorial/how-to-install-fail2ban-on-centos/

I can't remember the other one. I have removed all of the manual amendments
so am now basically set up as initially installed.

/var/log/fail2ban.log is showing that it's working:

2019-04-26 11:41:08,850 fail2ban.filter [7853]: INFO [dovecot] Found
155.133.4.195
2019-04-26 11:41:09,651 fail2ban.filter [7853]: INFO [dovecot] Found
185.222.209.56
2019-04-26 11:41:11,397 fail2ban.filter [7853]: INFO [dovecot] Found
185.222.209.56
2019-04-26 11:41:11,909 fail2ban.filter [7853]: INFO [dovecot] Found
185.222.209.56
2019-04-26 11:41:12,873 fail2ban.actions [7853]: NOTICE [dovecot] 185.222.209.56
already banned
2019-04-26 11:41:24,306 fail2ban.filter [7853]: INFO [dovecot] Found
185.222.209.56
2019-04-26 11:41:25,010 fail2ban.filter [7853]: INFO [dovecot] Found
46.232.112.21
2019-04-26 11:41:36,035 fail2ban.filter [7853]: INFO [dovecot] Found
46.232.112.21
2019-04-26 11:41:40,564 fail2ban.filter [7853]: INFO [dovecot] Found
45.227.253.100
2019-04-26 11:41:50,779 fail2ban.filter [7853]: INFO [dovecot] Found
45.227.253.100
2019-04-26 11:41:50,915 fail2ban.actions [7853]: NOTICE [dovecot] 45.227.253.100
already banned
2019-04-26 11:43:23,603 fail2ban.filter [7853]: INFO [dovecot] Found
185.36.81.165
2019-04-26 11:43:24,016 fail2ban.actions [7853]: NOTICE [dovecot] 185.36.81.165
already banned
2019-04-26 11:44:09,734 fail2ban.filter [7853]: INFO [dovecot] Found
45.227.253.100
2019-04-26 11:44:19,887 fail2ban.filter [7853]: INFO [dovecot] Found
45.227.253.100

and yet the IP is still getting through to exim:

2019-04-26 11:41:39 dovecot_plain authenticator failed for ([46.232.112.21])
[46.232.112.21]: 535 Incorrect authentication data (set_id=aa26fa5)
2019-04-26 11:41:44 dovecot_plain authenticator failed for ([45.227.253.100])
[45.227.253.100]: 535 Incorrect authentication data (set_id=*********)
2019-04-26 11:41:55 dovecot_plain authenticator failed for ([45.227.253.100])
[45.227.253.100]: 535 Incorrect authentication data (set_id=********)
2019-04-26 11:43:27 dovecot_login authenticator failed for (88.211.105.31)
[185.36.81.165]: 535 Incorrect authentication data (set_id=**********)
2019-04-26 11:44:13 dovecot_plain authenticator failed for ([45.227.253.100])
[45.227.253.100]: 535 Incorrect authentication data (set_id=****************)
2019-04-26 11:44:23 dovecot_plain authenticator failed for ([45.227.253.100])
[45.227.253.100]: 535 Incorrect authentication data (set_id=****************)
2019-04-26 11:45:19 dovecot_plain authenticator failed for ([185.222.209.56])
[185.222.209.56]: 535 Incorrect authentication data (set_id=****************)
2019-04-26 11:45:35 dovecot_plain authenticator failed for ([185.222.209.56])
[185.222.209.56]: 535 Incorrect authentication data (set_id=****************)
2019-04-26 11:46:36 dovecot_plain authenticator failed for ([185.222.209.56])
[185.222.209.56]: 535 Incorrect authentication data (set_id=****************)
2019-04-26 11:46:37 dovecot_plain authenticator failed for ([45.227.253.100])
[45.227.253.100]: 535 Incorrect authentication data (set_id=****************)

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