Detection: Detect Password Spray Attempts

 1
 2| tstats `security_content_summariesonly` dc(Authentication.user) AS unique_accounts values(Authentication.app) as app count(Authentication.user) as total_failures from datamodel=Authentication.Authentication where Authentication.action="failure" by Authentication.src, Authentication.action, Authentication.signature_id, sourcetype, _time  span=2m 
 3| `drop_dm_object_name("Authentication")` ```fill out time buckets for 0-count events during entire search length``` 
 4| appendpipe [
 5| timechart limit=0 span=5m count 
 6| table _time] 
 7| fillnull value=0 unique_accounts, unique_src ``` remove duplicate & empty time buckets``` 
 8| sort - total_failures 
 9| dedup _time ``` Create aggregation field & apply to all null events``` 
10| eval counter=src+"__"+sourcetype+"__"+signature_id 
11| eventstats values(counter) as fnscounter 
12| eval counter=coalesce(counter,fnscounter) 
13| eventstats avg(unique_accounts) as comp_avg , stdev(unique_accounts) as comp_std by counter 
14| eval upperBound=(comp_avg+comp_std*3) 
15| eval isOutlier=if(unique_accounts > 30 and unique_accounts >= upperBound, 1, 0) 
16| replace "::ffff:*" with * in src 
17| where isOutlier=1 
18| foreach * [ eval <<FIELD>> = if(<<FIELD>>="null",null(),<<FIELD>>)] 
19| table _time, src, action, app, unique_accounts, total_failures, sourcetype, signature_id 
20| `detect_password_spray_attempts_filter`