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Description

This search will detect users creating spikes in API activity related to network access-control lists (ACLs)in your AWS environment. This search is deprecated and have been translated to use the latest Change Datamodel.

  • Type: Anomaly

  • Product: Splunk Enterprise, Splunk Enterprise Security, Splunk Cloud

  • Last Updated: 2018-05-21
  • Author: Bhavin Patel, Splunk
  • ID: ada0f478-84a8-4641-a1f1-e32372d4bd53

Annotations

ATT&CK
ID Technique Tactic
T1562.007 Disable or Modify Cloud Firewall Defense Evasion
Kill Chain Phase
  • Actions on Objectives
NIST
  • DE.DP
  • DE.CM
  • PR.AC
CIS20
  • CIS 12
  • CIS 11
CVE 
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`cloudtrail` `network_acl_events` [search `cloudtrail` `network_acl_events` 
| spath output=arn path=userIdentity.arn 
| stats count as apiCalls by arn 
| inputlookup network_acl_activity_baseline append=t 
| fields - latestCount 
| stats values(*) as * by arn 
| rename apiCalls as latestCount 
| eval newAvgApiCalls=avgApiCalls + (latestCount-avgApiCalls)/720 
| eval newStdevApiCalls=sqrt(((pow(stdevApiCalls, 2)*719 + (latestCount-newAvgApiCalls)*(latestCount-avgApiCalls))/720)) 
| eval avgApiCalls=coalesce(newAvgApiCalls, avgApiCalls), stdevApiCalls=coalesce(newStdevApiCalls, stdevApiCalls), numDataPoints=if(isnull(latestCount), numDataPoints, numDataPoints+1) 
| table arn, latestCount, numDataPoints, avgApiCalls, stdevApiCalls 
| outputlookup network_acl_activity_baseline 
| eval dataPointThreshold = 15, deviationThreshold = 3 
| eval isSpike=if((latestCount > avgApiCalls+deviationThreshold*stdevApiCalls) AND numDataPoints > dataPointThreshold, 1, 0) 
| where isSpike=1 
| rename arn as userIdentity.arn 
| table userIdentity.arn] 
| spath output=user userIdentity.arn 
| stats values(eventName) as eventNames, count as numberOfApiCalls, dc(eventName) as uniqueApisCalled by user 
| `detect_spike_in_network_acl_activity_filter`

Macros

The SPL above uses the following Macros:

Note that detect_spike_in_network_acl_activity_filter is a empty macro by default. It allows the user to filter out any results (false positives) without editing the SPL.

Lookups

The SPL above uses the following Lookups:

Required field

  • _time
  • userIdentity.arn

How To Implement

You must install the AWS App for Splunk (version 5.1.0 or later) and Splunk Add-on for AWS (version 4.4.0 or later), then configure your AWS CloudTrail inputs. You can modify dataPointThreshold and deviationThreshold to better fit your environment. The dataPointThreshold variable is the minimum number of data points required to have a statistically significant amount of data to determine. The deviationThreshold variable is the number of standard deviations away from the mean that the value must be to be considered a spike. This search works best when you run the “Baseline of Network ACL Activity by ARN” support search once to create a lookup file of previously seen Network ACL Activity. To add or remove API event names related to network ACLs, edit the macro network_acl_events.

Known False Positives

The false-positive rate may vary based on the values ofdataPointThreshold and deviationThreshold. Please modify this according the your environment.

Associated Analytic story

RBA

Risk Score Impact Confidence Message
25.0 50 50 tbd

Reference

Test Dataset

Replay any dataset to Splunk Enterprise by using our replay.py tool or the UI. Alternatively you can replay a dataset into a Splunk Attack Range

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