Azure Storage Account Public Network Access Enabled

Severity: high
Log types: Azure.MonitorActivity
Tags: Exfiltration, Exfiltration Over Web Service
Reference: https://www.mitiga.io/blog/ransomware-strikes-azure-storage-are-you-ready
Source: github.com/panther-labs/panther-analysis

Detects when an existing Azure storage account's network settings are modified to enable public network access. This could indicate a potential data exfiltration risk or misconfiguration.

MITRE ATT&CK coverage

Tactic	Techniques
Exfiltration	`T1567` Exfiltration Over Web Service

Rule body yaml

AnalysisType: rule
Filename: azure_storage_account_public_network_access_enabled.py
RuleID: "Azure.MonitorActivity.StorageAccount.PublicNetworkAccessEnabled"
DisplayName: "Azure Storage Account Public Network Access Enabled"
Enabled: true
LogTypes:
  - Azure.MonitorActivity
Severity: High
Description: >
  Detects when an existing Azure storage account's network settings are modified to enable public network access.
  This could indicate a potential data exfiltration risk or misconfiguration.
Reports:
  MITRE ATT&CK:
    - TA0010:T1567 # Exfiltration: Exfiltration Over Web Service
Tags:
  - Exfiltration
  - Exfiltration Over Web Service
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 establish activity patterns
  2. Check if the source IP is associated with known cloud providers, VPN services, or corporate network ranges using threat intelligence
  3. Search for other Azure storage account modifications or data access events from the same user or IP in the past 7 days to identify potential data exfiltration campaigns
Reference: https://www.mitiga.io/blog/ransomware-strikes-azure-storage-are-you-ready
SummaryAttributes:
  - resourceId
  - callerIpAddress
  - correlationId
Tests:
  - Name: Public 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",
        "resultSignature": "200",
        "durationMs": 1523,
        "callerIpAddress": "1.1.1.1",
        "correlationId": "a1b2c3d4-e5f6-7890-abcd-ef1234567890",
        "identity": {
          "claims": {
            "name": "denethor@lotr.com"
          }
        },
        "level": "Informational",
        "location": "eastus",
        "properties": {
          "requestbody": "{\"properties\":{\"networkAcls\":{\"defaultAction\":\"Allow\",\"bypass\":\"AzureServices\",\"virtualNetworkRules\":[],\"ipRules\":[]}}}"
        },
        "tenantId": "87654321-4321-4321-4321-111111111111"
      }
  - Name: Case Insensitive Match
    ExpectedResult: true
    Log:
      {
        "time": "2024-12-17T11:45:00.0000000Z",
        "resourceId": "/subscriptions/12345678-1234-1234-1234-123456789abc/resourceGroups/prod-rg/providers/Microsoft.Storage/storageAccounts/prodstorage",
        "operationName": "microsoft.storage/storageaccounts/write",
        "operationVersion": "2021-04-01",
        "category": "Administrative",
        "resultType": "Succeeded",
        "callerIpAddress": "1.2.3.4",
        "correlationId": "f9e8d7c6-b5a4-3210-9876-fedcba098765",
        "properties": {
          "requestbody": "{\"properties\":{\"networkAcls\":{\"defaultAction\":\"Allow\"}}}"
        },
        "tenantId": "87654321-4321-4321-4321-111111111111"
      }
  - Name: Different Operation
    ExpectedResult: false
    Log:
      {
        "time": "2024-12-17T09:15:00.0000000Z",
        "resourceId": "/subscriptions/12345678-1234-1234-1234-123456789abc/resourceGroups/myresourcegroup/providers/Microsoft.Storage/storageAccounts/newstorageaccount",
        "operationName": "Microsoft.Storage/storageAccounts/write",
        "operationVersion": "2021-04-01",
        "category": "Administrative",
        "resultType": "Success",
        "callerIpAddress": "4.4.4.4",
        "correlationId": "b2c3d4e5-f6a7-8901-bcde-f12345678901",
        "properties": {
          "requestbody": "{\"location\":\"westus\",\"properties\":{\"networkAcls\":{\"defaultAction\":\"Allow\"}}}"
        },
        "tenantId": "87654321-4321-4321-4321-111111111111"
      }

Detection logic

Condition

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

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`
`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)