topic Re: How to exclude events with same session_id - Remote Desktop Network Bruteforce in Splunk Enterprise Security

How to exclude events with same session_id - Remote Desktop Network Bruteforce?

jmgonzalez — Fri, 26 Aug 2022 14:22:53 GMT

Hello,

We are trying to modify the existing query in the "Remote Desktop Network Bruteforce" correlation search present in the Splunk ES use cases to exclude events with the same session_id.

The original query is:

| tstats `security_content_summariesonly` count min(_time) as firstTime max(_time) as lastTime from datamodel=Network_Traffic where All_Traffic.app=rdp by All_Traffic.src All_Traffic.dest All_Traffic.dest_port | eventstats stdev(count) AS stdev avg(count) AS avg p50(count) AS p50 | where count>(avg + stdev*2) | rename All_Traffic.src AS src All_Traffic.dest AS dest | table firstTime lastTime src dest count avg p50 stdev | `remote_desktop_network_bruteforce_filter`

We have tried using the "dedup" command and the "distinct_count" function of stats command without success.
Thanks in advance,
Best Regards,

Re: How to exclude events with same session_id - Remote Desktop Network Bruteforce

richgalloway — Thu, 18 Aug 2022 12:50:35 GMT

The tstats command does not provide the session_id field so you won't be able to filter on it. You'll have to modify the query so tstats returns session_id then you can include the field in your `remote_desktop_network_bruteforce_filter` macro.

Re: How to exclude events with same session_id - Remote Desktop Network Bruteforce

jmgonzalez — Wed, 24 Aug 2022 15:24:45 GMT

After including the "session_id" field within the tstats command, in the BY clause to extract it, we have observed that some results are excluded where there are several different values in the session_id field.

Re: How to exclude events with same session_id - Remote Desktop Network Bruteforce

hettervik — Fri, 26 Aug 2022 14:13:29 GMT

Note that "session_id" is not an eval field in the Network Traffic data model, meaning that it could be null for some entries. If you add session_id to the by clause, these entries would be dismissed. If this is the case, you can either use the "fillnull_value" argument on the tstats command, or instead of adding session_id after the by clause, add it as a values function.

| tstats summariesonly=t count values(All_Traffic.session_id) as session_id min(_time) as firstTime max(_time) as lastTime from datamodel=Network_Traffic by All_Traffic.src All_Traffic.dest All_Traffic.dest_port