S3 bucket exposed via ACL

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Id	6b9b4ee6-f4c1-4b86-8c8c-beb0bb59ae44
Rulename	S3 bucket exposed via ACL
Description	Detected S3 bucket publicly exposed via ACL, which could lead for sensitive information leakage to the public. Verify the S3 object configurations.
Severity	Medium
Tactics	Exfiltration
Techniques	T1537
Required data connectors	AWS
Kind	Scheduled
Query frequency	1h
Query period	1h
Trigger threshold	0
Trigger operator	gt
Source Uri	https://github.com/Azure/Azure-Sentinel/blob/master/Solutions/Amazon Web Services/Analytic Rules/AWS_S3BucketExposedviaACL.yaml
Version	1.0.1
Arm template	6b9b4ee6-f4c1-4b86-8c8c-beb0bb59ae44.json

KQL

AWSCloudTrail
| where EventName == "PutBucketAcl" and isempty(ErrorCode) and isempty(ErrorMessage)
| extend UserIdentityArn = iif(isempty(UserIdentityArn), tostring(parse_json(Resources)[0].ARN), UserIdentityArn)
| extend UserName = tostring(split(UserIdentityArn, '/')[-1])
| extend AccountName = case( UserIdentityPrincipalid == "Anonymous", "Anonymous", isempty(UserIdentityUserName), UserName, UserIdentityUserName)
| extend AccountName = iif(AccountName contains "@", tostring(split(AccountName, '@', 0)[0]), AccountName),
  AccountUPNSuffix = iif(AccountName contains "@", tostring(split(AccountName, '@', 1)[0]), "")
| extend Grant = parse_json(tostring((parse_json(RequestParameters).AccessControlPolicy))).AccessControlList.Grant
| mvexpand Grant
| extend cannedacl = parse_json(tostring((parse_json(RequestParameters))))
| extend URI = parse_json(Grant).Grantee.URI, type = parse_json(Grant).Grantee.["xsi:type"], xamzacl = parse_json(cannedacl).["x-amz-acl"]
| where (type == "Group" and (URI endswith "AllUsers" or URI endswith "AuthenticatedUsers"))
  or xamzacl in ("authenticated-read","public-read","public-read-write")
| extend timestamp = TimeGenerated

YAML

status: Available
queryFrequency: 1h
description: |
    'Detected S3 bucket publicly exposed via ACL, which could lead for sensitive information leakage to the public. Verify the S3 object configurations.'
severity: Medium
version: 1.0.1
relevantTechniques:
- T1537
name: S3 bucket exposed via ACL
triggerThreshold: 0
kind: Scheduled
query: |
  AWSCloudTrail
  | where EventName == "PutBucketAcl" and isempty(ErrorCode) and isempty(ErrorMessage)
  | extend UserIdentityArn = iif(isempty(UserIdentityArn), tostring(parse_json(Resources)[0].ARN), UserIdentityArn)
  | extend UserName = tostring(split(UserIdentityArn, '/')[-1])
  | extend AccountName = case( UserIdentityPrincipalid == "Anonymous", "Anonymous", isempty(UserIdentityUserName), UserName, UserIdentityUserName)
  | extend AccountName = iif(AccountName contains "@", tostring(split(AccountName, '@', 0)[0]), AccountName),
    AccountUPNSuffix = iif(AccountName contains "@", tostring(split(AccountName, '@', 1)[0]), "")
  | extend Grant = parse_json(tostring((parse_json(RequestParameters).AccessControlPolicy))).AccessControlList.Grant
  | mvexpand Grant
  | extend cannedacl = parse_json(tostring((parse_json(RequestParameters))))
  | extend URI = parse_json(Grant).Grantee.URI, type = parse_json(Grant).Grantee.["xsi:type"], xamzacl = parse_json(cannedacl).["x-amz-acl"]
  | where (type == "Group" and (URI endswith "AllUsers" or URI endswith "AuthenticatedUsers"))
    or xamzacl in ("authenticated-read","public-read","public-read-write")
  | extend timestamp = TimeGenerated  
triggerOperator: gt
OriginalUri: https://github.com/Azure/Azure-Sentinel/blob/master/Solutions/Amazon Web Services/Analytic Rules/AWS_S3BucketExposedviaACL.yaml
requiredDataConnectors:
- connectorId: AWS
  dataTypes:
  - AWSCloudTrail
tactics:
- Exfiltration
id: 6b9b4ee6-f4c1-4b86-8c8c-beb0bb59ae44
queryPeriod: 1h
entityMappings:
- fieldMappings:
  - columnName: AccountName
    identifier: Name
  - columnName: AccountUPNSuffix
    identifier: UPNSuffix
  - columnName: RecipientAccountId
    identifier: CloudAppAccountId
  entityType: Account
- fieldMappings:
  - columnName: SourceIpAddress
    identifier: Address
  entityType: IP

ARM

{
  "$schema": "https://schema.management.azure.com/schemas/2019-04-01/deploymentTemplate.json#",
  "contentVersion": "1.0.0.0",
  "parameters": {
    "workspace": {
      "type": "String"
    }
  },
  "resources": [
    {
      "apiVersion": "2024-01-01-preview",
      "id": "[concat(resourceId('Microsoft.OperationalInsights/workspaces/providers', parameters('workspace'), 'Microsoft.SecurityInsights'),'/alertRules/6b9b4ee6-f4c1-4b86-8c8c-beb0bb59ae44')]",
      "kind": "Scheduled",
      "name": "[concat(parameters('workspace'),'/Microsoft.SecurityInsights/6b9b4ee6-f4c1-4b86-8c8c-beb0bb59ae44')]",
      "properties": {
        "alertRuleTemplateName": "6b9b4ee6-f4c1-4b86-8c8c-beb0bb59ae44",
        "customDetails": null,
        "description": "'Detected S3 bucket publicly exposed via ACL, which could lead for sensitive information leakage to the public. Verify the S3 object configurations.'\n",
        "displayName": "S3 bucket exposed via ACL",
        "enabled": true,
        "entityMappings": [
          {
            "entityType": "Account",
            "fieldMappings": [
              {
                "columnName": "AccountName",
                "identifier": "Name"
              },
              {
                "columnName": "AccountUPNSuffix",
                "identifier": "UPNSuffix"
              },
              {
                "columnName": "RecipientAccountId",
                "identifier": "CloudAppAccountId"
              }
            ]
          },
          {
            "entityType": "IP",
            "fieldMappings": [
              {
                "columnName": "SourceIpAddress",
                "identifier": "Address"
              }
            ]
          }
        ],
        "OriginalUri": "https://github.com/Azure/Azure-Sentinel/blob/master/Solutions/Amazon Web Services/Analytic Rules/AWS_S3BucketExposedviaACL.yaml",
        "query": "AWSCloudTrail\n| where EventName == \"PutBucketAcl\" and isempty(ErrorCode) and isempty(ErrorMessage)\n| extend UserIdentityArn = iif(isempty(UserIdentityArn), tostring(parse_json(Resources)[0].ARN), UserIdentityArn)\n| extend UserName = tostring(split(UserIdentityArn, '/')[-1])\n| extend AccountName = case( UserIdentityPrincipalid == \"Anonymous\", \"Anonymous\", isempty(UserIdentityUserName), UserName, UserIdentityUserName)\n| extend AccountName = iif(AccountName contains \"@\", tostring(split(AccountName, '@', 0)[0]), AccountName),\n  AccountUPNSuffix = iif(AccountName contains \"@\", tostring(split(AccountName, '@', 1)[0]), \"\")\n| extend Grant = parse_json(tostring((parse_json(RequestParameters).AccessControlPolicy))).AccessControlList.Grant\n| mvexpand Grant\n| extend cannedacl = parse_json(tostring((parse_json(RequestParameters))))\n| extend URI = parse_json(Grant).Grantee.URI, type = parse_json(Grant).Grantee.[\"xsi:type\"], xamzacl = parse_json(cannedacl).[\"x-amz-acl\"]\n| where (type == \"Group\" and (URI endswith \"AllUsers\" or URI endswith \"AuthenticatedUsers\"))\n  or xamzacl in (\"authenticated-read\",\"public-read\",\"public-read-write\")\n| extend timestamp = TimeGenerated\n",
        "queryFrequency": "PT1H",
        "queryPeriod": "PT1H",
        "severity": "Medium",
        "status": "Available",
        "subTechniques": [],
        "suppressionDuration": "PT1H",
        "suppressionEnabled": false,
        "tactics": [
          "Exfiltration"
        ],
        "techniques": [
          "T1537"
        ],
        "templateVersion": "1.0.1",
        "triggerOperator": "GreaterThan",
        "triggerThreshold": 0
      },
      "type": "Microsoft.OperationalInsights/workspaces/providers/alertRules"
    }
  ]
}