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Description

The following analytic identifies a spike in the number of AWS Security Hub alerts for an EC2 instance within a 4-hour interval. It leverages AWS Security Hub findings data, calculating the average and standard deviation of alerts to detect anomalies. This activity is significant for a SOC as a sudden increase in alerts may indicate potential security incidents or misconfigurations requiring immediate attention. If confirmed malicious, this could signify an ongoing attack, leading to unauthorized access, data exfiltration, or disruption of services on the affected EC2 instance.

  • Type: Anomaly

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

  • Last Updated: 2024-05-19
  • Author: Bhavin Patel, Splunk
  • ID: 2a9b80d3-6340-4345-b5ad-290bf5d0d222

Annotations

ATT&CK
Kill Chain Phase
NIST
  • DE.AE
CIS20
  • CIS 10
CVE 


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`aws_securityhub_finding` "Resources{}.Type"=AWSEC2Instance 
| bucket span=4h _time 
| stats count AS alerts values(Title) as Title values(Types{}) as Types values(vendor_account) as vendor_account values(vendor_region) as vendor_region values(severity) as severity by _time dest 
| eventstats avg(alerts) as total_alerts_avg, stdev(alerts) as total_alerts_stdev 
| eval threshold_value = 3 
| eval isOutlier=if(alerts > total_alerts_avg+(total_alerts_stdev * threshold_value), 1, 0) 
| search isOutlier=1 
| table _time dest alerts Title Types vendor_account vendor_region severity isOutlier total_alerts_avg 
| `detect_spike_in_aws_security_hub_alerts_for_ec2_instance_filter`

Macros

The SPL above uses the following Macros:

:information_source: detect_spike_in_aws_security_hub_alerts_for_ec2_instance_filter is a empty macro by default. It allows the user to filter out any results (false positives) without editing the SPL.

Required fields

List of fields required to use this analytic.

  • _time
  • Resources{}.Type
  • Title
  • Types{}
  • vendor_account
  • vendor_region
  • severity
  • dest

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 Security Hub inputs. The threshold_value should be tuned to your environment and schedule these searches according to the bucket span interval.

Known False Positives

None

Associated Analytic Story

RBA

Risk Score Impact Confidence Message
15.0 30 50 Spike in AWS security Hub alerts with title $Title$ for EC2 instance $dest$

:information_source: The Risk Score is calculated by the following formula: Risk Score = (Impact * Confidence/100). Initial Confidence and Impact is set by the analytic author.

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

source | version: 4