Azure Storage File Share Created or Modified

Severity: informational
Log types: Azure.MonitorActivity
Tags: Exfiltration, Exfiltration Over Alternative Protocol, Collection, Data from Cloud Storage, AZT702, AZT702.1, File Share Mounting, Storage Account File Share NFS/SMB Mount
Reference: https://microsoft.github.io/Azure-Threat-Research-Matrix/Impact/AZT702/AZT702-1
Source: github.com/panther-labs/panther-analysis

Detects when an Azure Storage file share is created or modified. File shares can be mounted as network drives using SMB or NFS protocols, providing persistent access to storage. Adversaries may create or modify file shares to establish data exfiltration channels or mount shares to local systems for easier data transfer. While file share operations are common in legitimate scenarios, monitoring these activities helps establish baselines and identify unusual patterns that may indicate data exfiltration.

MITRE ATT&CK coverage

Tactic	Techniques
Collection	`T1530` Data from Cloud Storage
Exfiltration	`T1048` Exfiltration Over Alternative Protocol

Rule body yaml

AnalysisType: rule
Filename: azure_storage_fileshare_modified.py
RuleID: "Azure.MonitorActivity.Storage.FileShareModified"
DisplayName: "Azure Storage File Share Created or Modified"
Enabled: true
LogTypes:
  - Azure.MonitorActivity
Severity: Info
Description: >
  Detects when an Azure Storage file share is created or modified. File shares can be mounted as
  network drives using SMB or NFS protocols, providing persistent access to storage. Adversaries may
  create or modify file shares to establish data exfiltration channels or mount shares to local systems
  for easier data transfer. While file share operations are common in legitimate scenarios, monitoring
  these activities helps establish baselines and identify unusual patterns that may indicate data exfiltration.
Reports:
  MITRE ATT&CK:
    - TA0010:T1048 # Exfiltration: Exfiltration Over Alternative Protocol
    - TA0009:T1530 # Collection: Data from Cloud Storage
Tags:
  - Exfiltration
  - Exfiltration Over Alternative Protocol
  - Collection
  - Data from Cloud Storage
  - AZT702
  - AZT702.1
  - File Share Mounting
  - Storage Account File Share NFS/SMB Mount
Runbook: |
  1. Find all storage account operations by the callerIpAddress in the 6 hours before and after this alert to identify if this is part of a data staging or exfiltration pattern
  2. Query for the storage account configuration to determine if the file share has public access or is restricted to specific networks
  3. Check if the callerIpAddress has created or modified file shares in the past 30 days to determine if this is normal administrative behavior
Reference: https://microsoft.github.io/Azure-Threat-Research-Matrix/Impact/AZT702/AZT702-1
SummaryAttributes:
  - resourceId
  - callerIpAddress
  - correlationId
Tests:
  - Name: File Share Created
    ExpectedResult: true
    Log:
      {
        "time": "2025-12-23T10:30:00.0000000Z",
        "resourceId": "/subscriptions/12345678-1234-1234-1234-123456789abc/resourceGroups/storage-rg/providers/Microsoft.Storage/storageAccounts/mystorageaccount/fileServices/default/shares/data-share",
        "operationName": "Microsoft.Storage/storageAccounts/fileServices/shares/write",
        "operationVersion": "2021-09-01",
        "category": "Administrative",
        "resultType": "Success",
        "resultSignature": "201",
        "callerIpAddress": "1.1.1.1",
        "correlationId": "a1b2c3d4-e5f6-7890-abcd-ef1234567890",
        "level": "Informational",
        "location": "eastus",
        "tenantId": "87654321-4321-4321-4321-111111111111"
      }
  - Name: File Share Modified
    ExpectedResult: true
    Log:
      {
        "time": "2025-12-23T11:00:00.0000000Z",
        "resourceId": "/subscriptions/11111111-1111-1111-1111-111111111111/resourceGroups/prod-rg/providers/Microsoft.Storage/storageAccounts/prodstorage/fileServices/default/shares/backup-share",
        "operationName": "Microsoft.Storage/storageAccounts/fileServices/shares/write",
        "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/app-rg/providers/Microsoft.Storage/storageAccounts/appstorage/fileServices/default/shares/app-data",
        "operationName": "microsoft.storage/storageaccounts/fileservices/shares/write",
        "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: Different Operation
    ExpectedResult: false
    Log:
      {
        "time": "2025-12-23T16:00:00.0000000Z",
        "resourceId": "/subscriptions/77777777-7777-7777-7777-777777777777/resourceGroups/storage-rg/providers/Microsoft.Storage/storageAccounts/storage/fileServices/default/shares/share",
        "operationName": "Microsoft.Storage/storageAccounts/fileServices/shares/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.STORAGE/STORAGEACCOUNTS/FILESERVICES/SHARES/WRITE"
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.STORAGE/STORAGEACCOUNTS/FILESERVICES/SHARES/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)