detection.wiki

Detection rules › Kusto

API - BOLA

Status
available
Severity
medium
Time window
5m
Source
github.com/Azure/Azure-Sentinel

'42Crunch API protection against BOLA'

MITRE ATT&CK coverage

TacticTechniques
Exfiltration

Rule body

id: 1b047dc3-a879-4f99-949b-d1dc867efc83
name: API - BOLA
description: |
  '42Crunch API protection against BOLA'
severity: Medium
requiredDataConnectors:
  - connectorId: 42CrunchAPIProtection
    dataTypes:
      - FortyTwoCrunchAPIProtection
  - connectorId: FortyTwoCrunchAPIProtection
    dataTypes:
      - FortyTwoCrunchAPIProtection
queryFrequency: 5m
queryPeriod: 5m
triggerOperator: gt
triggerThreshold: 0
eventGroupingSettings:
  aggregationKind: SingleAlert
status: Available
tactics:
  - Exfiltration
relevantTechniques:
  - T1020
query: |
  let loginRec = FortyTwoCrunchAPIProtection
  | where TimeGenerated >= ago(5m) 
  | project-away NonBlockingMode, SourcePort, DestinationPort, Query, ApiId, RequestHeader, ResponseHeader, Errors, EventType, Uuid
  | where UriPath has "/api/login" and Status == 200;
  let ipAddress = toscalar(loginRec
  | top 1 by Timestamp desc
  | summarize by SourceIp);
  let listRec = FortyTwoCrunchAPIProtection
  | where TimeGenerated >= ago(5m) 
  | project-away NonBlockingMode, SourcePort, DestinationPort, Query, ApiId, RequestHeader, ResponseHeader, Errors, EventType, Uuid
  | where UriPath has "/api/accounts/list" and Status == 200;
  let listCnt = (toscalar(listRec | count));
  let accountRec = FortyTwoCrunchAPIProtection
  | where TimeGenerated >= ago(5m) 
  | project-away NonBlockingMode, SourcePort, DestinationPort, Query, ApiId, RequestHeader, ResponseHeader, Errors, EventType, Uuid
  | where SourceIp == ipAddress and UriPath matches regex "/api/accounts/\\d{6}$";
  let accountCnt = (toscalar(accountRec | count));
  let recCount = iff((toscalar(listRec | count) == 0) and (accountCnt > 5), accountCnt, 0);
  accountRec | take recCount
customDetails:
entityMappings:
  - entityType: IP
    fieldMappings:
      - identifier: Address
        columnName: SourceIp
  - entityType: Host
    fieldMappings:
      - identifier: HostName
        columnName: Hostname
  - entityType: Account
    fieldMappings:
      - identifier: FullName
        columnName: InstanceName
version: 3.0.1
kind: Scheduled

Stages and Predicates

let accountRec is inlined into the numbered stages below.

Let binding: loginRec

let loginRec = FortyTwoCrunchAPIProtection
| where TimeGenerated >= ago(5m) 
| project-away NonBlockingMode, SourcePort, DestinationPort, Query, ApiId, RequestHeader, ResponseHeader, Errors, EventType, Uuid
| where UriPath has "/api/login" and Status == 200;

Let binding: ipAddress used in Stage 4

let ipAddress = toscalar(loginRec
| top 1 by Timestamp desc
| summarize by SourceIp);

Let binding: listRec

let listRec = FortyTwoCrunchAPIProtection
| where TimeGenerated >= ago(5m) 
| project-away NonBlockingMode, SourcePort, DestinationPort, Query, ApiId, RequestHeader, ResponseHeader, Errors, EventType, Uuid
| where UriPath has "/api/accounts/list" and Status == 200;

Let binding: listCnt

let listCnt = (toscalar(listRec | count));

Let binding: accountCnt

let accountCnt = (toscalar(accountRec | count));

Let binding: recCount used in Stage 5

let recCount = iff((toscalar(listRec | count) == 0) and (accountCnt > 5), accountCnt, 0);

Stages 1 to 4 define let accountRec (the rule's main pipeline source); stage 5 runs on it.

Stage 1: source

FortyTwoCrunchAPIProtection

Stage 2: where

| where TimeGenerated >= ago(5m)

Stage 3: project-away

| project-away NonBlockingMode, SourcePort, DestinationPort, Query, ApiId, RequestHeader, ResponseHeader, Errors, EventType, Uuid

Stage 4: where

| where SourceIp == ipAddress and UriPath matches regex "/api/accounts/\\d{6}$"

Stage 5: take

accountRec
| take recCount

Indicators

These rows show field, operator, and value matches.

FieldKindValuesSearch
SourceIpcross_field_compare
  • ipAddress transforms: op:eq
field:"src_ip" kind:cross_field_compare value:"ipAddress"
UriPathregex_match
  • /api/accounts/\d{6}$
field:"UriPath" kind:regex_match value:"/api/accounts/\d{6}$"