Detection: Crowdstrike Medium Severity Alert

Updated Date: 2024-09-30 ID: 7e80d92a-6ec3-4eb1-a444-1480acfe2d14 Author: Teoderick Contreras, Splunk Type: Anomaly Product: Splunk Enterprise Security

Description

The following analytic detects a CrowdStrike alert with MEDIUM severity indicates a potential threat that requires prompt attention. This alert level suggests suspicious activity that may compromise security but is not immediately critical. It typically involves detectable but non-imminent risks, such as unusual behavior or attempted policy violations, which should be investigated further and mitigated quickly to prevent escalation of attacks.

Search

1`crowdstrike_stream` 
2| rename event.EndpointIp as src_ip, event.EndpointName as src_host, event.UserName as user, event.IncidentDescription as description, event.IncidentType as type, event.NumbersOfAlerts as count_alerts, event.SeverityName as severity 
3| stats count min(_time) as firstTime max(_time) as lastTime by src_ip, src_host, user, description, type, count_alerts, severity 
4| where LIKE (severity, "%MEDIUM%") 
5| `security_content_ctime(firstTime)` 
6| `security_content_ctime(lastTime)` 
7| `crowdstrike_medium_severity_alert_filter`

Data Source

No data sources specified for this detection.

Macros Used

Name	Value
crowdstrike_stream	`sourcetype="CrowdStrike:Event:Streams:JSON"`
crowdstrike_medium_severity_alert_filter	`search *`

crowdstrike_medium_severity_alert_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
T1110	Brute Force	Credential Access

KillChainPhase.EXPLOITAITON

NistCategory.DE_AE

Cis18Value.CIS_10

APT28

APT38

APT39

APT41

Agrius

DarkVishnya

Dragonfly

Ember Bear

FIN5

Fox Kitten

HEXANE

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

To implement CrowdStrike stream JSON logs, use the Falcon Streaming API. Set up an API client, authenticate with your CrowdStrike credentials, and subscribe to the "CrowdStrike:Event:Streams:JSON" event stream. Process and store the JSON logs as needed, integrating them into your logging or SIEM system for monitoring and analysis.

Known False Positives

unknown

Associated Analytic Story

Compromised Windows Host

Risk Based Analytics (RBA)

Risk Message	Risk Score	Impact	Confidence
A MEDIUM Severity Crowdstrike Alert found in $src_host$	49	70	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

https://www.crowdstrike.com/wp-content/uploads/2022/12/CrowdStrike-Falcon-Event-Streams-Add-on-Guide-v3.pdf

Detection Testing

Test Type	Status	Dataset	Source	Sourcetype
Validation	✅ Passing	N/A	N/A	N/A
Unit	✅ Passing	Dataset	`CrowdStrike:Event:Streams`	`CrowdStrike:Event:Streams:JSON`
Integration	✅ Passing	Dataset	`CrowdStrike:Event:Streams`	`CrowdStrike:Event:Streams:JSON`

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