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Description

The following analytic identifies an AWS account with more than 20 failed authentication events in the span of 5 minutes. This behavior could represent a brute force attack against the account. As environments differ across organizations, security teams should customize the threshold of this detection.

  • Type: Anomaly

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

  • Last Updated: 2023-01-27
  • Author: Bhavin Patel, Splunk
  • ID: e3236f49-daf3-4b70-b808-9290912ac64d

Annotations

ATT&CK

ATT&CK

ID Technique Tactic
T1201 Password Policy Discovery Discovery
Kill Chain Phase
  • Exploitation
NIST
  • DE.AE
CIS20
  • CIS 10
CVE 


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2
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`cloudtrail` eventName=ConsoleLogin action=failure 
| bucket span=10m _time 
| stats dc(_raw) AS failed_attempts values(src_ip) as src_ip values(user_agent) by _time, user_name, eventName, eventSource aws_account_id 
| where failed_attempts > 20 
| `aws_high_number_of_failed_authentications_for_user_filter`

Macros

The SPL above uses the following Macros:

:information_source: aws_high_number_of_failed_authentications_for_user_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
  • eventName
  • userAgent
  • errorCode
  • requestParameters.userName
  • eventSource
  • user_arn
  • aws_account_id
  • src_ip

How To Implement

You must install Splunk AWS Add on and Splunk App for AWS. This search works with AWS CloudTrail logs.

Known False Positives

A user with more than 20 failed authentication attempts in the span of 5 minutes may also be triggered by a broken application.

Associated Analytic Story

RBA

Risk Score Impact Confidence Message
35.0 50 70 User $user_name$ failed to authenticate more than 20 times in the span of 5 minutes for AWS Account $aws_account_id$

: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

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