Azure Storage Blob Bulk Extraction

Severity: medium
Log types: Azure.MonitorActivity
Tags: Exfiltration, Collection, Storm-0501, Defender for Cloud, Data Theft
Reference: https://learn.microsoft.com/en-us/azure/defender-for-cloud/alerts-azure-storage
Source: github.com/panther-labs/panther-analysis

Detects high-volume blob extraction (50+ GetBlob operations in 15 minutes) from Azure Storage accounts. Storm-0501 rapidly extracts data using stolen credentials before ransomware deployment. Replicates Defender for Cloud alert 'Unusual amount of data extracted from a storage account'.

MITRE ATT&CK coverage

Tactic	Techniques
Collection	`T1530` Data from Cloud Storage
Exfiltration	`T1567` Exfiltration Over Web Service

Rule body yaml

AnalysisType: rule
Filename: azure_storage_blob_bulk_extraction.py
RuleID: "Azure.MonitorActivity.Storage.Blob.BulkExtraction"
DisplayName: "Azure Storage Blob Bulk Extraction"
Enabled: true
LogTypes:
  - Azure.MonitorActivity
Severity: Medium
Threshold: 50
DedupPeriodMinutes: 15
Description: >
  Detects high-volume blob extraction (50+ GetBlob operations in 15 minutes) from Azure Storage accounts.
  Storm-0501 rapidly extracts data using stolen credentials before ransomware deployment.
  Replicates Defender for Cloud alert 'Unusual amount of data extracted from a storage account'.
Reports:
  MITRE ATT&CK:
    - TA0010:T1567 # Exfiltration: Exfiltration Over Web Service
    - TA0009:T1530 # Collection: Data from Cloud Storage
Reference: https://learn.microsoft.com/en-us/azure/defender-for-cloud/alerts-azure-storage
Tags:
  - Exfiltration
  - Collection
  - Storm-0501
  - Defender for Cloud
  - Data Theft
Runbook: |
  1. Query Azure MonitorActivity logs for all GetBlob operations from the callerIpAddress in the 2 hours before and after the alert to calculate total blob count
  2. Compare the blob count from step 1 to the callerIpAddress's 30-day average for this storage account to determine if this is anomalous volume
  3. Find all SAS token generation operations (listAccountSas, listServiceSas) in the 6 hours before the first GetBlob to identify if stolen SAS tokens are being used
  4. Check if the callerIpAddress has accessed this storage account in the past 90 days to determine if this is a new or known accessor
  5. Search for authentication events from the callerIpAddress in Azure.Audit logs in the 48 hours before the alert to assess if account compromise preceded the extraction
SummaryAttributes:
  - callerIpAddress
  - resourceId
  - properties:objectKey
Tests:
  - Name: Successful Blob Extraction
    ExpectedResult: true
    Log:
      {
        "time": "2025-01-28T18:00:00.000Z",
        "resourceId": "/subscriptions/12345678-1234-1234-1234-123456789abc/resourceGroups/myresourcegroup/providers/Microsoft.Storage/storageAccounts/mystorageaccount/blobServices/default",
        "operationName": "GetBlob",
        "callerIpAddress": "8.8.8.8:44321",
        "location": "eastus",
        "category": "StorageRead",
        "level": "Informational",
        "properties": {
          "accountName": "mystorageaccount",
          "clientRequestId": "b1c2d3e4-f5g6-7890-hijk-lm9876543210",
          "metricResponseType": "Success",
          "objectKey": "/mystorageaccount/sensitive-data/financials/report_2025.xlsx",
          "serverLatencyMs": 18,
          "serviceType": "blob",
          "tlsVersion": "TLS 1.3",
          "userAgentHeader": "python-requests/2.31.0"
        },
        "tenantId": "87654321-4321-4321-4321-111111111111",
        "p_log_type": "Azure.MonitorActivity"
      }
  - Name: Case Insensitive Match
    ExpectedResult: true
    Log:
      {
        "time": "2025-01-28T18:00:05.000Z",
        "resourceId": "/subscriptions/12345678-1234-1234-1234-123456789abc/resourceGroups/myresourcegroup/providers/Microsoft.Storage/storageAccounts/mystorageaccount/blobServices/default",
        "operationName": "getblob",
        "callerIpAddress": "1.1.1.1:55443",
        "location": "eastus",
        "properties": {
          "accountName": "mystorageaccount",
          "metricResponseType": "Success",
          "objectKey": "/mystorageaccount/backups/database_backup.bak",
          "userAgentHeader": "curl/8.4.0"
        },
        "tenantId": "87654321-4321-4321-4321-111111111111",
        "p_log_type": "Azure.MonitorActivity"
      }
  - Name: Different Operation
    ExpectedResult: false
    Log:
      {
        "time": "2025-01-28T18:01:00.000Z",
        "resourceId": "/subscriptions/12345678-1234-1234-1234-123456789abc/resourceGroups/myresourcegroup/providers/Microsoft.Storage/storageAccounts/mystorageaccount/blobServices/default",
        "operationName": "PutBlob",
        "callerIpAddress": "10.0.0.1:42781",
        "location": "eastus",
        "properties": {
          "accountName": "mystorageaccount",
          "metricResponseType": "Success",
          "objectKey": "/mystorageaccount/uploads/data.json"
        },
        "tenantId": "87654321-4321-4321-4321-210987654321",
        "p_log_type": "Azure.MonitorActivity"
      }
  - Name: Failed Operation
    ExpectedResult: false
    Log:
      {
        "time": "2025-01-28T18:02:00.000Z",
        "resourceId": "/subscriptions/12345678-1234-1234-1234-123456789abc/resourceGroups/myresourcegroup/providers/Microsoft.Storage/storageAccounts/mystorageaccount/blobServices/default",
        "operationName": "GetBlob",
        "callerIpAddress": "9.9.9.9:33333",
        "location": "eastus",
        "properties": {
          "accountName": "mystorageaccount",
          "metricResponseType": "AuthorizationFailure",
          "objectKey": "/mystorageaccount/secrets/config.json"
        },
        "tenantId": "87654321-4321-4321-4321-111111111111",
        "p_log_type": "Azure.MonitorActivity"
      }

Detection logic

Condition

operationName eq "GETBLOB"
properties.metricResponseType eq "Success"

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	`GETBLOB`
`properties.metricResponseType`	eq	`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)