Azure VM Disk SAS URI Generated

Severity: high
Log types: Azure.MonitorActivity
Tags: AZT701.1, Exfiltration, Collection, Exfiltration Over Web Service, Exfiltration to Cloud Storage, Data from Cloud Storage
Reference: https://microsoft.github.io/Azure-Threat-Research-Matrix/Impact/AZT701/AZT701-1
Source: github.com/panther-labs/panther-analysis

Detects when a Shared Access Signature (SAS) URI is generated for an Azure VM disk. SAS URIs provide time-limited, unauthenticated access to download disk contents directly from Azure Storage. Adversaries can generate SAS URIs to exfiltrate entire virtual machine disks, including operating systems, applications, and all data. This allows offline analysis to extract credentials, secrets, and sensitive data without detection. This is a critical indicator of data exfiltration and should be investigated immediately.

MITRE ATT&CK coverage

Tactic	Techniques
Collection	`T1530` Data from Cloud Storage
Exfiltration	`T1567.002` Exfiltration Over Web Service: Exfiltration to Cloud Storage

Rule body yaml

AnalysisType: rule
Filename: azure_vm_disk_sas_uri_generated.py
RuleID: "Azure.MonitorActivity.Compute.DiskSASURIGenerated"
DisplayName: "Azure VM Disk SAS URI Generated"
Enabled: true
LogTypes:
  - Azure.MonitorActivity
Severity: High
Description: >
  Detects when a Shared Access Signature (SAS) URI is generated for an Azure VM disk.
  SAS URIs provide time-limited, unauthenticated access to download disk contents directly from Azure Storage.
  Adversaries can generate SAS URIs to exfiltrate entire virtual machine disks, including operating systems,
  applications, and all data. This allows offline analysis to extract credentials, secrets, and sensitive data
  without detection. This is a critical indicator of data exfiltration and should be investigated immediately.
Reports:
  MITRE ATT&CK:
    - TA0010:T1567.002 # Exfiltration: Exfiltration Over Web Service - Exfiltration to Cloud Storage
    - TA0009:T1530 # Collection: Data from Cloud Storage
Tags:
  - AZT701.1
  - Exfiltration
  - Collection
  - Exfiltration Over Web Service
  - Exfiltration to Cloud Storage
  - Data from Cloud Storage
Runbook: |
  1. Find all disk and storage operations by the callerIpAddress in the 24 hours before and after this alert to identify if multiple disks are being exfiltrated
  2. Query for the VM associated with this disk to determine what applications and data are stored on the disk
  3. Check if the callerIpAddress has performed similar disk export operations in the past 90 days to determine if this is expected backup behavior
Reference: https://microsoft.github.io/Azure-Threat-Research-Matrix/Impact/AZT701/AZT701-1
SummaryAttributes:
  - resourceId
  - callerIpAddress
  - correlationId
Tests:
  - Name: SAS URI Generated for Disk
    ExpectedResult: true
    Log:
      {
        "time": "2025-12-23T10:30:00.0000000Z",
        "resourceId": "/subscriptions/12345678-1234-1234-1234-123456789abc/resourceGroups/vm-rg/providers/Microsoft.Compute/disks/vm-prod-osdisk",
        "operationName": "Microsoft.Compute/disks/beginGetAccess/action",
        "operationVersion": "2021-04-01",
        "category": "Administrative",
        "resultType": "Success",
        "resultSignature": "200",
        "callerIpAddress": "1.1.1.1",
        "correlationId": "a1b2c3d4-e5f6-7890-abcd-ef1234567890",
        "level": "Informational",
        "location": "eastus",
        "tenantId": "87654321-4321-4321-4321-111111111111"
      }
  - Name: Disk Export with Succeeded Status
    ExpectedResult: true
    Log:
      {
        "time": "2025-12-23T11:00:00.0000000Z",
        "resourceId": "/subscriptions/11111111-1111-1111-1111-111111111111/resourceGroups/prod-rg/providers/Microsoft.Compute/disks/database-server-disk",
        "operationName": "Microsoft.Compute/disks/beginGetAccess/action",
        "category": "Administrative",
        "resultType": "Succeeded",
        "callerIpAddress": "2.2.2.2",
        "correlationId": "b2c3d4e5-f6a7-8901-bcde-f12345678901",
        "level": "Information",
        "location": "westeurope",
        "tenantId": "22222222-2222-2222-2222-222222222222"
      }
  - Name: Case Insensitive Match
    ExpectedResult: true
    Log:
      {
        "time": "2025-12-23T12:00:00.0000000Z",
        "resourceId": "/subscriptions/33333333-3333-3333-3333-333333333333/resourceGroups/security-rg/providers/Microsoft.Compute/disks/web-server-data-disk",
        "operationName": "microsoft.compute/disks/begingetaccess/action",
        "category": "Administrative",
        "resultType": "Success",
        "callerIpAddress": "3.3.3.3",
        "correlationId": "c3d4e5f6-a7b8-9012-cdef-333333333333",
        "level": "Informational",
        "location": "centralus",
        "tenantId": "33333333-3333-3333-3333-333333333333"
      }
  - Name: Data Disk SAS Generation
    ExpectedResult: true
    Log:
      {
        "time": "2025-12-23T13:00:00.0000000Z",
        "resourceId": "/subscriptions/44444444-4444-4444-4444-444444444444/resourceGroups/app-rg/providers/Microsoft.Compute/disks/app-server-datadisk-001",
        "operationName": "Microsoft.Compute/disks/beginGetAccess/action",
        "category": "Administrative",
        "resultType": "Success",
        "callerIpAddress": "4.4.4.4",
        "correlationId": "d4e5f6a7-b8c9-0123-def0-444444444444",
        "level": "Informational",
        "location": "westus",
        "tenantId": "44444444-4444-4444-4444-444444444444"
      }
  - Name: Different Operation
    ExpectedResult: false
    Log:
      {
        "time": "2025-12-23T16:00:00.0000000Z",
        "resourceId": "/subscriptions/77777777-7777-7777-7777-777777777777/resourceGroups/vm-rg/providers/Microsoft.Compute/disks/vm-disk",
        "operationName": "Microsoft.Compute/disks/read",
        "category": "Administrative",
        "resultType": "Success",
        "callerIpAddress": "7.7.7.7",
        "correlationId": "a7b8c9d0-e1f2-3456-0123-777777777777",
        "tenantId": "77777777-7777-7777-7777-777777777777"
      }

Detection logic

Condition

operationName in "MICROSOFT.COMPUTE/DISKS/BEGINGETACCESS/ACTION"
resultType in ["Success", "Succeeded"]

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`	in	`MICROSOFT.COMPUTE/DISKS/BEGINGETACCESS/ACTION`
`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)