Detection: AWS High Number Of Failed Authentications For User

Updated Date: 2024-05-25 ID: e3236f49-daf3-4b70-b808-9290912ac64d Author: Bhavin Patel, Splunk Type: Anomaly Product: Splunk Enterprise Security

Description

The following analytic detects an AWS account experiencing more than 20 failed authentication attempts within a 5-minute window. It leverages AWS CloudTrail logs to identify multiple failed ConsoleLogin events. This behavior is significant as it may indicate a brute force attack targeting the account. If confirmed malicious, the attacker could potentially gain unauthorized access, leading to data breaches or further exploitation of the AWS environment. Security teams should consider adjusting the threshold based on their specific environment to reduce false positives.

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

Data Source

Name Platform Sourcetype Source Supported App
AWS CloudTrail ConsoleLogin AWS icon AWS 'aws:cloudtrail' 'aws_cloudtrail' N/A

Macros Used

Name Value
cloudtrail sourcetype=aws:cloudtrail
aws_high_number_of_failed_authentications_for_user_filter search *
aws_high_number_of_failed_authentications_for_user_filter is an empty macro by default. It allows the user to filter out any results (false positives) without editing the SPL.

Annotations

- MITRE ATT&CK
+ Kill Chain Phases
+ NIST
+ CIS
- Threat Actors
ID Technique Tactic
T1201 Password Policy Discovery Discovery
KillChainPhase.EXPLOITAITON
NistCategory.DE_AE
Cis18Value.CIS_10
Chimera
OilRig
Turla

Default Configuration

This detection is configured by default in Splunk Enterprise Security to run with the following settings:

Setting Value
Disabled true
Cron Schedule 0 * * * *
Earliest Time -70m@m
Latest Time -10m@m
Schedule Window auto
Creates Risk Event True
This configuration file applies to all detections of type anomaly. These detections will use Risk Based Alerting.

Implementation

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

Risk Based Analytics (RBA)

Risk Message Risk Score Impact Confidence
User $user_name$ failed to authenticate more than 20 times in the span of 5 minutes for AWS Account $aws_account_id$ 35 50 70
The Risk Score is calculated by the following formula: Risk Score = (Impact * Confidence/100). Initial Confidence and Impact is set by the analytic author.

References

Detection Testing

Test Type Status Dataset Source Sourcetype
Validation ✅ Passing N/A N/A N/A
Unit ✅ Passing Dataset aws_cloudtrail aws:cloudtrail
Integration ✅ Passing Dataset aws_cloudtrail aws:cloudtrail

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: GitHub | Version: 2