On Sep 20, 2013 11:45 AM, "Paul Raines" <[email protected]> wrote:
>
> I have recently started using ossec and I am trying to filter out bogus
> alerts from my httpd access_log without success.
>
> I often get email alerts with:
>
> Received From: (surfer) 132.183.202.158->/var/log/httpd/access_log
> Rule: 1002 fired (level 2) -> "Unknown problem somewhere in the system."
> Portion of the log(s):
>
> 141.39.166.146, 129.187.254.46 - - [20/Sep/2013:05:21:39 -0400] "GET
> /pub/docs/fsl2013/freesurfer.failure_modes.ppt HTTP/1.0" 200 5633536 80
> "
http://surfer.nmr.mgh.harvard.edu/fswiki/FsTutorial/June2013FslCourseSchedu
> le" "Mozilla/5.0 (Windows NT 5.1) AppleWebKit/537.36 (KHTML, like Gecko)
> Chrome/28.0.1500.95 Safari/537.36"
>
> Now, the fact that there are two IPS at the start of log line I am sure
> is the crux of the problem.  That happens due to the Varnish Cache
> accelerator in use that proxies in front of Apache.  Sometimes my log
> has lines starting like:
>
> - - - [07/Sep/2013:04:15:03 -0400] "GET ...." 200 ...
>
> where the IP for some reason is lost.
>
> Firstly, since this is the apache web log, I don't even understand why
> rule 1002 from syslog is being applied (which triggers on the word
> "failure" in the name of the PPT file).  Can someone explain why?

A keyword (fail) is found in the log message.

> In fact I don't understand for a given <localfile> definition how
> the system decides which decoders apply.  Does it just apply all of
> them till it finds a match?  That is why the syslog decoder ends up
> being applied?
>

I believe this is (very basically) correct.

> I know the proper way probably to deal with this is for me to
> modify the apache-accesslog decoder to handle the missing or multiple
> IP issue.  But to try to put in a quick filter I tried adding to
> local_rules.xml inside <group name="local,syslog,"> the lines
>
>   <rule id="100303" level="0">
>     <if_sid>1002</if_sid>
>     <description>Ignore successful HTML GETs</description>
>     <regex>HTTP/1....200</regex>

Why are you using the regex option without actually putting any regex in it?

>   </rule>
>
> but this has done nothing to ignore alerts like the one above.
> Any idea what I am doing wrong?
>
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