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Unable to follow Step 10 of Security Investigation Online Experience Endpoint Example

wuming79
Path Finder

Hi,

I'm doing the exercise at https://www.splunk.com/blog/2017/05/13/steering-clear-of-the-wannacry-or-wanna-decryptor-ransomware-....

Step 10 was to search for the following syntax:
sourcetype=xmlwineventlog:microsoft-windows-sysmon/operational EventCode=1
| eval cmdlen=len(CommandLine)
| eventstats avg(cmdlen) as avg, stdev(cmdlen) as stdev by host
| stats max(cmdlen) as maxlen, values(avg) as avgperhost, values(stdev) as stdevperhost by host, CommandLine
| eval threshold = 4 * ( stdevperhost + avgperhost )
| where maxlen > threshold

Example returned an event with maxlen = 4490 but when I tried it on the "Launch Online Session" with the same search, I cannotfind that event.

I went to analyze the logs again and found that the maxlen is only 309. Step 1 to Step 9 were very accurate. What did I do wrong??

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0 Karma

jbrodsky_splunk
Splunk Employee
Splunk Employee

Hello again @wuming79. Your issue in the first screenshot above is that the "top" command is finding the "most prolific command line length values in the dataset" and NOT the "largest command line length value in the dataset."

To demonstrate this point, try this:

sourcetype=xmlwineventlog:microsoft-windows-sysmon/operational EventCode=1  
| eval cmdlen=len(CommandLine)  
| fields cmdlen
| sort -cmdlen
| table cmdlen
| dedup cmdlen
| head 20

Or maybe this link.

0 Karma
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