Azure Storage Blob Anonymous Access Enabled

Severity: high
Log types: Azure.MonitorActivity
Tags: Exfiltration, Data from Cloud Storage
Reference: https://hackingthe.cloud/azure/anonymous-blob-access/
Source: github.com/panther-labs/panther-analysis

Detects when Azure storage account blob anonymous access is enabled at the account level or when container public access is configured. Enabling anonymous access allows unauthenticated users to read blob data and may lead to data exposure.

MITRE ATT&CK coverage

Tactic	Techniques
Collection	`T1530` Data from Cloud Storage

Rule body yaml

AnalysisType: rule
Filename: azure_storage_blob_anonymous_access_enabled.py
RuleID: "Azure.MonitorActivity.StorageAccount.BlobAnonymousAccessEnabled"
DisplayName: "Azure Storage Blob Anonymous Access Enabled"
Enabled: true
LogTypes:
  - Azure.MonitorActivity
Severity: High
Description: >
  Detects when Azure storage account blob anonymous access is enabled at the account level or when container public access is configured.
  Enabling anonymous access allows unauthenticated users to read blob data and may lead to data exposure.
Reports:
  MITRE ATT&CK:
    - TA0010:T1530 # Exfiltration: Data from Cloud Storage
Tags:
  - Exfiltration
  - Data from Cloud Storage
Runbook: |
  1. Query Azure Monitor Activity logs for all storage account operations by the callerIpAddress in the 6 hours before and after this alert to identify if this is part of a broader configuration change
  2. Check if the source IP is associated with known cloud providers, VPN services, or corporate network ranges using threat intelligence
  3. Search for data access patterns or blob download events from the affected storage account in the 24 hours after this configuration change to identify potential data exposure
Reference: https://hackingthe.cloud/azure/anonymous-blob-access/
SummaryAttributes:
  - resourceId
  - callerIpAddress
  - correlationId
Tests:
  - Name: Storage Account Anonymous Access Enabled
    ExpectedResult: true
    Log:
      {
        "time": "2024-12-17T10:30:00.0000000Z",
        "resourceId": "/subscriptions/12345678-1234-1234-1234-123456789abc/resourceGroups/myresourcegroup/providers/Microsoft.Storage/storageAccounts/mystorageaccount",
        "operationName": "Microsoft.Storage/storageAccounts/write",
        "operationVersion": "2021-04-01",
        "category": "Administrative",
        "resultType": "Success",
        "callerIpAddress": "1.1.1.1",
        "location": "eastus",
        "correlationId": "a1b2c3d4-e5f6-7890-abcd-ef1234567890",
        "properties": {
          "requestbody": "{\"properties\":{\"allowBlobPublicAccess\":true}}"
        },
        "tenantId": "87654321-4321-4321-4321-111111111111"
      }
  - Name: Storage Account Anonymous Access Disabled
    ExpectedResult: false
    Log:
      {
        "time": "2024-12-17T11:00:00.0000000Z",
        "resourceId": "/subscriptions/12345678-1234-1234-1234-123456789abc/resourceGroups/myresourcegroup/providers/Microsoft.Storage/storageAccounts/securestorageaccount",
        "operationName": "Microsoft.Storage/storageAccounts/write",
        "operationVersion": "2021-04-01",
        "category": "Administrative",
        "resultType": "Success",
        "callerIpAddress": "2.2.2.2",
        "location": "eastus",
        "correlationId": "b2c3d4e5-f6a7-8901-bcde-f12345678901",
        "properties": {
          "requestbody": "{\"properties\":{\"allowBlobPublicAccess\":false}}"
        },
        "tenantId": "87654321-4321-4321-4321-111111111111"
      }
  - Name: Container Public Access Set to Blob
    ExpectedResult: true
    Log:
      {
        "time": "2024-12-17T12:00:00.0000000Z",
        "resourceId": "/subscriptions/12345678-1234-1234-1234-123456789abc/resourceGroups/myresourcegroup/providers/Microsoft.Storage/storageAccounts/mystorageaccount/blobServices/default/containers/mycontainer",
        "operationName": "Microsoft.Storage/storageAccounts/blobServices/containers/write",
        "operationVersion": "2021-04-01",
        "category": "Administrative",
        "resultType": "Success",
        "callerIpAddress": "3.3.3.3",
        "location": "eastus",
        "correlationId": "c3d4e5f6-a7b8-9012-cdef-444444444444",
        "properties": {
          "requestbody": "{\"properties\":{\"publicAccess\":\"Blob\"}}"
        },
        "tenantId": "87654321-4321-4321-4321-111111111111"
      }
  - Name: Container Public Access Set to Container
    ExpectedResult: true
    Log:
      {
        "time": "2024-12-17T13:00:00.0000000Z",
        "resourceId": "/subscriptions/12345678-1234-1234-1234-123456789abc/resourceGroups/myresourcegroup/providers/Microsoft.Storage/storageAccounts/mystorageaccount/blobServices/default/containers/publiccontainer",
        "operationName": "Microsoft.Storage/storageAccounts/blobServices/containers/write",
        "operationVersion": "2021-04-01",
        "category": "Administrative",
        "resultType": "Success",
        "callerIpAddress": "4.4.4.4",
        "location": "westus",
        "correlationId": "d4e5f6a7-b8c9-0123-def0-333333333333",
        "properties": {
          "requestbody": "{\"properties\":{\"publicAccess\":\"Container\"}}"
        },
        "tenantId": "87654321-4321-4321-4321-111111111111"
      }
  - Name: Container Public Access Set to None
    ExpectedResult: false
    Log:
      {
        "time": "2024-12-17T14:00:00.0000000Z",
        "resourceId": "/subscriptions/12345678-1234-1234-1234-123456789abc/resourceGroups/myresourcegroup/providers/Microsoft.Storage/storageAccounts/securestorageaccount/blobServices/default/containers/privatecontainer",
        "operationName": "Microsoft.Storage/storageAccounts/blobServices/containers/write",
        "operationVersion": "2021-04-01",
        "category": "Administrative",
        "resultType": "Success",
        "callerIpAddress": "5.5.5.5",
        "location": "eastus",
        "correlationId": "e5f6a7b8-c9d0-1234-ef01-222222222222",
        "properties": {
          "requestbody": "{\"properties\":{\"publicAccess\":\"None\"}}"
        },
        "tenantId": "87654321-4321-4321-4321-111111111111"
      }
  - Name: Different Operation
    ExpectedResult: false
    Log:
      {
        "time": "2024-12-17T16:00:00.0000000Z",
        "resourceId": "/subscriptions/12345678-1234-1234-1234-123456789abc/resourceGroups/myresourcegroup/providers/Microsoft.Storage/storageAccounts/mystorageaccount",
        "operationName": "Microsoft.Storage/storageAccounts/delete",
        "operationVersion": "2021-04-01",
        "category": "Administrative",
        "resultType": "Success",
        "callerIpAddress": "7.7.7.7",
        "location": "eastus",
        "correlationId": "a7b8c9d0-e1f2-3456-0123-567890123456",
        "tenantId": "87654321-4321-4321-4321-111111111111"
      }

Detection logic

Condition

resultType in ["Success", "Succeeded"]
operationName eq "MICROSOFT.STORAGE/STORAGEACCOUNTS/WRITE" or operationName in ["MICROSOFT.STORAGE/STORAGEACCOUNTS/BLOBSERVICES/WRITE", "MICROSOFT.STORAGE/STORAGEACCOUNTS/BLOBSERVICES/CONTAINERS/WRITE"]

This rule also runs imperative logic the parser cannot express as a filter; the conditions above are the structured part it could extract.

Indicators

Each row is a field, operator, and value that the rule matches. The corpus column counts how many other rules in the catalog look for the same combination: high numbers point to widely-used, community-vetted indicators. Blank or 1 shows that the indicator is specific to this rule.

Field	Kind	Values
`operationName`	eq	`MICROSOFT.STORAGE/STORAGEACCOUNTS/WRITE`
`operationName`	in	`MICROSOFT.STORAGE/STORAGEACCOUNTS/BLOBSERVICES/CONTAINERS/WRITE` `MICROSOFT.STORAGE/STORAGEACCOUNTS/BLOBSERVICES/WRITE`
`resultType`	in	`Succeeded` `Success`

`j` / `k`	Scroll down / up
`d` / `u`	Half-page down / up
`gg` / `G`	Top / bottom
`h` / `l`	History back / forward
`f`	Follow link (`Shift` = new tab)
`/`	Focus search
`?`	Toggle this help
`↑` / `↓`	Navigate search results
`Enter`	Open highlighted result
`Esc`	Close results / dialog

`type:`	`events` / `rules` / `providers`
`vendor:`	`sigma` / `elastic` / `splunk` / `kusto` / `chronicle` (vendor name alone also works: `sigma:`, `kql:`, `secops:`…)
`tactic:`	TA-id, slug, or name: `credential_access`, `TA0006`
`technique:`	technique or sub-technique ID: `T1003`, `T1003.001` (alias `tech:`)
`severity:`	`critical` / `high` / `medium` / `low` / `informational` (alias `sev:`)
`risk_score`	Numeric comparison on the Elastic risk score (0 to 100): `risk_score>50`, `risk_score<=20`, `risk_score=99` (alias `risk`; Elastic rules only)
`stages:`	Rules with exactly N pipeline stages
`correlation:`	`single_event` / `sequence` / `alternatives` / `alternatives_cross_log` / `all_required` / `correlated`
`with:`	Co-occurrence event-id; stacks (`with:4624 with:4769`) to require all, while a comma list in one occurrence (`with:4624,4769`) is an either-or group. Implies multi-event
`like:`	Structural neighbors of a rule slug (equivalents + subsumption stricter / broader): `like:comsvcs_lsass_memory_dump-splunk-sysmon`
`groupby:`	Entity-grouping substring match against `group_by_keys`: `groupby:user`, `groupby:host`
`uses:`	Rules whose predicate tree touches the field (any kind, any value): `uses:CommandLine`
`excludes:`	Rules with top-level `not()` clauses on the field (FP whitelists): `excludes:ParentImage`
`field:` / `value:`	Predicate search; narrows rule cards to those with a matching leaf and drives the indicator tier. Unquoted = substring, wildcards allowed (`value:mimikatz`)
`indicator:`	Shorthand for `field:F value:V`: `indicator:Image=*\powershell.exe`
`kind:`	Filter by predicate kind. Narrows rule cards to those carrying a matching predicate leaf (`vendor:elastic kind:cidr_match`) and drives the indicator tier: `contains` / `starts_with` / `ends_with` / `regex` / `cidr` / `eq` / `in` … (operator aliases `op:`/`match:`)
`has:` / `no:`	`sample`, `field`, `notes`, `refs`, `trace`, `thirdparty`, `rule`, `pattern`, `timewindow`, `threshold`, `newterms`, `sigma`/`elastic`/`splunk`/`kusto`/`chronicle`
`-op:val`	Exclude matches; works on most operators but not `type:`/`like:`/`has:`/`no:` (use `no:<flag>` to exclude a rule flag): `tactic:execution -vendor:splunk`. Standalone `-kind:`/`-field:`/`-value:` drop every rule carrying a matching predicate leaf (`type:rules -kind:is_null`)
`field:"…"` / `value:"…"`	Quoted value = anchored exact match (also allows spaces): `value:"net user"`
`a,b`	Comma = OR inside one operator (`vendor:sigma,elastic`, `severity:high,critical`); repeating a facet merges the same way. `field:`/`value:` never split (literal commas)
`vendors:` / `stage:`	Singular and plural spellings fold to the canonical operator and value: `tactics:` = `tactic:`, `type:event` = `type:events`, `correlation:sequences` = `correlation:sequence`, `has:thresholds` = `has:threshold`
`"quoted phrase"`	Exact-match a multi-word phrase (free text)