Brute force attack against user credentials Uses Authentication Normalization

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Id	a6c435a2-b1a0-466d-b730-9f8af69262e8
Rulename	Brute force attack against user credentials (Uses Authentication Normalization)
Description	Identifies evidence of brute force activity against a user based on multiple authentication failures and at least one successful authentication within a given time window. Note that the query does not enforce any sequence, and does not require the successful authentication to occur last. The default failure threshold is 10, success threshold is 1, and the default time window is 20 minutes. To use this analytics rule, make sure you have deployed the ASIM normalization parsers
Severity	Medium
Tactics	CredentialAccess
Techniques	T1110
Kind	Scheduled
Query frequency	20m
Query period	20m
Trigger threshold	0
Trigger operator	gt
Source Uri	https://github.com/Azure/Azure-Sentinel/blob/master/Detections/ASimAuthentication/imAuthBruteForce.yaml
Version	1.2.5
Arm template	a6c435a2-b1a0-466d-b730-9f8af69262e8.json

KQL

let failureCountThreshold = 10;
let successCountThreshold = 1;
// let authenticationWindow = 20m; // Implicit in the analytic rule query period 
imAuthentication
| where TargetUserType != "NonInteractive"
| summarize 
      StartTime = min(TimeGenerated), 
      EndTime = max(TimeGenerated), 
      IpAddresses = make_set (SrcDvcIpAddr, 100),
      ReportedBy = make_set (strcat (EventVendor, "/", EventProduct), 100),
      FailureCount = countif(EventResult=='Failure'),
      SuccessCount = countif(EventResult=='Success')
  by 
      TargetUserId, TargetUsername, TargetUserType 
| where FailureCount >= failureCountThreshold and SuccessCount >= successCountThreshold
| extend
      IpAddresses = strcat_array(IpAddresses, ", "), 
      ReportedBy = strcat_array(ReportedBy, ", ")
| extend
  Name = iif(
      TargetUsername contains "@"
          , tostring(split(TargetUsername, '@', 0)[0])
          , TargetUsername
      ),
  UPNSuffix = iif(
      TargetUsername contains "@"
      , tostring(split(TargetUsername, '@', 1)[0])
      , ""
  )

YAML

OriginalUri: https://github.com/Azure/Azure-Sentinel/blob/master/Detections/ASimAuthentication/imAuthBruteForce.yaml
queryPeriod: 20m
kind: Scheduled
name: Brute force attack against user credentials (Uses Authentication Normalization)
customDetails:
  IpAddresses: IpAddresses
  ReportedBy: ReportedBy
entityMappings:
- fieldMappings:
  - columnName: TargetUserName
    identifier: FullName
  - columnName: Name
    identifier: Name
  - columnName: UPNSuffix
    identifier: UPNSuffix
  entityType: Account
tactics:
- CredentialAccess
description: |
  'Identifies evidence of brute force activity against a user based on multiple authentication failures and at least one successful authentication within a given time window.
  Note that the query does not enforce any sequence, and does not require the successful authentication to occur last.
  The default failure threshold is 10, success threshold is 1, and the default time window is 20 minutes.
  To use this analytics rule, make sure you have deployed the [ASIM normalization parsers](https://aka.ms/ASimAuthentication)'  
severity: Medium
metadata:
  categories:
    domains:
    - Security - Others
    - Identity
  support:
    tier: Community
  source:
    kind: Community
  author:
    name: Ofer Shezaf
tags:
- Id: 28b42356-45af-40a6-a0b4-a554cdfd5d8a
  version: 1.0.0
- SchemaVersion: 0.1.0
  Schema: ASIMAuthentication
requiredDataConnectors: []
queryFrequency: 20m
triggerThreshold: 0
version: 1.2.5
query: |
  let failureCountThreshold = 10;
  let successCountThreshold = 1;
  // let authenticationWindow = 20m; // Implicit in the analytic rule query period 
  imAuthentication
  | where TargetUserType != "NonInteractive"
  | summarize 
        StartTime = min(TimeGenerated), 
        EndTime = max(TimeGenerated), 
        IpAddresses = make_set (SrcDvcIpAddr, 100),
        ReportedBy = make_set (strcat (EventVendor, "/", EventProduct), 100),
        FailureCount = countif(EventResult=='Failure'),
        SuccessCount = countif(EventResult=='Success')
    by 
        TargetUserId, TargetUsername, TargetUserType 
  | where FailureCount >= failureCountThreshold and SuccessCount >= successCountThreshold
  | extend
        IpAddresses = strcat_array(IpAddresses, ", "), 
        ReportedBy = strcat_array(ReportedBy, ", ")
  | extend
    Name = iif(
        TargetUsername contains "@"
            , tostring(split(TargetUsername, '@', 0)[0])
            , TargetUsername
        ),
    UPNSuffix = iif(
        TargetUsername contains "@"
        , tostring(split(TargetUsername, '@', 1)[0])
        , ""
    )  
relevantTechniques:
- T1110
id: a6c435a2-b1a0-466d-b730-9f8af69262e8
triggerOperator: gt

ARM