On Fri, Feb 9, 2018 at 1:37 PM, Eric <[email protected]> wrote:
> Thanks Bruce. I didn't think about doing it that way but it definitely
> works. I really wish OSSEC would allow ! regex or just a simple <not
> match>Blah</not match>.
>

If you're interested in adding this feature, we use github. You can
submit a pull request
at https://github.com/ossec/osec-hids

>
> On Friday, February 9, 2018 at 10:35:31 AM UTC-7, Bruce Westbrook wrote:
>>
>> Eric, short answer is unfortunately "no" (see my similar question recently
>> under the subject "Rule Exception - How?").  The only portion of a rule that
>> you can negate/exclude are for srcip and dstip (see
>> http://ossec-docs.readthedocs.io/en/latest/syntax/head_rules.html).
>>
>> What I've found is that to exclude a subset of items you need to create a
>> minimum of two rules.  The first rule to catch only what you want to
>> exclude, the second rule to capture all the rest.  A simple example to
>> simply ignore the ActiveSync log entries and do something with all the rest,
>> using your log line examples and the rule you posted (not sure what rule
>> #100210 is but assume it's to match the log lines for your rule):
>>
>> <!--  Rule to ignore ActiveSync logs -->
>> <rule id="100211" level="0">
>>    <if_sid>100210</if_sid>
>>    <match>Microsoft-Server-ActiveSync</match>
>>    <description>NOISE:  Ignore ActiveSync log entries.</description>
>> </rule>
>>
>> <!--  Rule to do something with all the other log lines -->
>> <rule id="100212" level="5">
>>    <if_sid>100210</if_sid>
>>    <regex>\.+\d+\s\w+.\[email protected]\.+ - 401 </regex>
>>    <description>Email authentication failure.</description>
>> </rule>
>>
>>
>> Hope that helps point you in the right direction.
>>
>>
>> On Friday, February 9, 2018 at 10:38:47 AM UTC-5, Eric wrote:
>>>
>>> Hello,
>>>
>>> I'm working on a few custom rules and I was wondering if there is a "not
>>> equal to" item within OSSEC custom rules that I can use. I have the
>>> following logs and I want everything but the ActiveSync ones.
>>>
>>> Feb  9 00:00:00 XXXXX 2018-02-09 04:59:52 10.13.1.15 POST
>>> /autodiscover/autodiscover.xml &CorrelationID=<empty>;; 443 -
>>> [email protected] X.X.X.X SfBForMac/16.13.184.0000+(Mac+OSX+10.12.6) - 401 1
>>> 2148074254 0
>>>
>>> Feb  9 00:00:00 XXXXX 2018-02-09 04:59:52 10.13.1.15 POST
>>> /EWS/Exchange.asmx &CorrelationID=<empty>;; 443 - [email protected] X.X.X.X
>>> SfBForMac/16.13.184.0000+(Mac+OSX+10.12.6) - 401 1 2148074254 0
>>>
>>> Feb  9 00:00:01 XXXXX 2018-02-09 04:59:58 10.13.1.28 POST
>>> /Microsoft-Server-ActiveSync/default.eas ; 443 [email protected] X.X.X.X
>>> Android-Mail/7.10.22.174510681.release - 200 0 0 15
>>>
>>> Right now I have the following logic and it works, but I'd prefer to just
>>> do a not equal to Activesync so I don't have to add additional regexes if a
>>> new log comes in.
>>>
>>> <rule id="100211" level="5">
>>>    <if_sid>100210</if_sid>
>>>    <regex>autodiscovery.xml|Exchange.asmx</regex>
>>>    <regex>\.+\d+\s\w+.\[email protected]\.+ - 401 </regex>
>>>    <description>Email authentication failure.</description>
>>> </rule>
>>>
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