Unusual Volume of file deletion by users

Status: available
Severity: high
Time window: 5m
Group by: AccountDisplayName, ActionType, ApplicationId, Time, UserId
Source: github.com/Azure/Azure-Sentinel

This query looks for users performing file deletion activities. Spikes in file deletion observed from risky sign-in sessions are flagged here. This applies to SharePoint and OneDrive users. Audit event and Cloud application identifier references. Reference - https://learn.microsoft.com/microsoft-365/compliance/audit-log-activities?view=o365-worldwide Reference - https://learn.microsoft.com/azure/sentinel/entities-reference#cloud-application-identifiers

MITRE ATT&CK coverage

Tactic	Techniques
Impact	`T1485` Data Destruction

Rule body kusto

id: e5f8e196-3544-4a8b-96a9-17c1b6a49710
name: Unusual Volume of file deletion by users
description: |
  This query looks for users performing file deletion activities. Spikes in file deletion observed from risky sign-in sessions are flagged here.
  This applies to SharePoint and OneDrive users.
  Audit event and Cloud application identifier references.
  Reference - https://learn.microsoft.com/microsoft-365/compliance/audit-log-activities?view=o365-worldwide
  Reference - https://learn.microsoft.com/azure/sentinel/entities-reference#cloud-application-identifiers
severity: High
status: Available
requiredDataConnectors:
  - connectorId: MicrosoftThreatProtection
    dataTypes:
      - CloudAppEvents
      - AADSignInEventsBeta
queryFrequency: 1h
queryPeriod: 1h
triggerOperator: gt
triggerThreshold: 0
tactics:
  - Impact
relevantTechniques:
  - T1485
query: |
  let relevantOperations = pack_array("FileDeleted", "FileRecycled", "FileDeletedFirstStageRecycleBin", "FileDeletedSecondStageRecycleBin", "FileVersionsAllMinorsRecycled", "FileVersionRecycled", "FileVersionsAllRecycled");
  let relevantAppIds = pack_array(int(20892), int(15600)); // App Ids for SharePoint and OneDrive
  let timeWindow = 7d;
  let timeNow = now();
  //
  let riskyUsers= // Look for users with risky sign-ins
    SigninLogs    
    | where CreatedDateTime between ((timeNow - timeWindow) .. (timeNow))
    | where isnotempty(UserId) and isnotempty(OriginalRequestId)
    | where ResultType == '0'
    | where RiskLevelDuringSignIn == 'high'
    | project RiskLevelDuringSignIn, UserId, CreatedDateTime, SessionId=OriginalRequestId
    ;
  let hasUsers = isnotempty(toscalar(riskyUsers));
  //
  let deleteEvents = // look for file deletion activity and scope it to risky users
    CloudAppEvents
    | where hasUsers
    | where TimeGenerated between ((timeNow - timeWindow) .. (timeNow))
    | where ApplicationId in (relevantAppIds)
    | where isnotempty(AccountObjectId)
    | where AccountObjectId in (riskyUsers)
    | where ActionType in (relevantOperations)
    | extend SessionId= tostring(RawEventData.AppAccessContext.AADSessionId)
    | where isnotempty(SessionId)
    | project UserId=AccountObjectId, AccountDisplayName, ApplicationId, SessionId, ActionType, TimeGenerated, ReportId
    ;   
   //
  deleteEvents  
  | join kind=leftsemi riskyUsers on UserId, SessionId
  | summarize Count=count() , (Timestamp, ReportId)=arg_min(TimeGenerated, ReportId) by UserId, AccountDisplayName, ApplicationId, ActionType, Time=bin(TimeGenerated, 5m)
  // look for only those scoped users who have generated an increase in file deletion activity.
  | summarize TotalCount= countif(Count > 50), (Timestamp, ReportId)=arg_min(Timestamp, ReportId) by UserId, AccountDisplayName, ApplicationId 
  | where TotalCount >= 3
  | project UserId, AccountDisplayName, ApplicationId, TotalCount, ReportId, Timestamp
  | extend NTDomain = tostring(split(AccountDisplayName,'\\',0)[0]), Name = tostring(split(AccountDisplayName,'\\',1)[0])
entityMappings:
  - entityType: Account
    fieldMappings:
      - identifier: AadUserId
        columnName: UserId
  - entityType: Account
    fieldMappings:
      - identifier: Name
        columnName: Name
      - identifier: NTDomain
        columnName: NTDomain
  - entityType: CloudApplication
    fieldMappings:
      - identifier: AppId
        columnName: ApplicationId
customDetails:
  Count: TotalCount
version: 1.0.1
kind: Scheduled

Stages and Predicates

Parameters

let relevantAppIds = pack_array(int(20892), int(15600));
let timeWindow = 7d;
let timeNow = now();
let hasUsers = isnotempty(toscalar(riskyUsers));

Let binding: `relevantOperations`

let relevantOperations = pack_array("FileDeleted", "FileRecycled", "FileDeletedFirstStageRecycleBin", "FileDeletedSecondStageRecycleBin", "FileVersionsAllMinorsRecycled", "FileVersionRecycled", "FileVersionsAllRecycled");

Let binding: `riskyUsers`

let riskyUsers = SigninLogs    
  | where CreatedDateTime between ((timeNow - timeWindow) .. (timeNow))
  | where isnotempty(UserId) and isnotempty(OriginalRequestId)
  | where ResultType == '0'
  | where RiskLevelDuringSignIn == 'high'
  | project RiskLevelDuringSignIn, UserId, CreatedDateTime, SessionId=OriginalRequestId;

Derived from timeWindow, timeNow.

The stages below define let deleteEvents (the rule's main pipeline source).

Stage 1: `source`

CloudAppEvents

Stage 2: `where`

| where hasUsers

Stage 3: `where`

| where TimeGenerated between ((timeNow - timeWindow) .. (timeNow))

Stage 4: `where`

| where ApplicationId in (relevantAppIds)

Stage 5: `where`

| where isnotempty(AccountObjectId)

Stage 6: `where`

| where AccountObjectId in (riskyUsers)

References riskyUsers (defined above).

Stage 7: `where`

| where ActionType in (relevantOperations)

References relevantOperations (defined above).

Stage 8: `extend`

| extend SessionId= tostring(RawEventData.AppAccessContext.AADSessionId)

Stage 9: `where`

| where isnotempty(SessionId)

Stage 10: `project`

| project UserId=AccountObjectId, AccountDisplayName, ApplicationId, SessionId, ActionType, TimeGenerated, ReportId

The stages below run on deleteEvents (the outer pipeline).

Stage 11: `join`

deleteEvents
| join kind=leftsemi riskyUsers on UserId, SessionId

Stage 12: `summarize`

| summarize Count=count() , (Timestamp, ReportId)=arg_min(TimeGenerated, ReportId) by UserId, AccountDisplayName, ApplicationId, ActionType, Time=bin(TimeGenerated, 5m)

Stage 13: `summarize`

| summarize TotalCount= countif(Count > 50), (Timestamp, ReportId)=arg_min(Timestamp, ReportId) by UserId, AccountDisplayName, ApplicationId

Threshold: ge 3

Stage 14: `where`

| where TotalCount >= 3

Stage 15: `project`

| project UserId, AccountDisplayName, ApplicationId, TotalCount, ReportId, Timestamp

Stage 16: `extend`

| extend NTDomain = tostring(split(AccountDisplayName,'\\',0)[0]), Name = tostring(split(AccountDisplayName,'\\',1)[0])

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
`AccountObjectId`	in	`riskyUsers` transforms: `cased`
`AccountObjectId`	is_not_null	(no value, null check)
`ActionType`	in	`relevantOperations` transforms: `cased`
`ApplicationId`	in	`relevantAppIds` transforms: `cased`
`OriginalRequestId`	is_not_null	(no value, null check)
`ResultType`	eq	`0` transforms: `cased` corpus 19 (kusto 17, sigma 2)
`RiskLevelDuringSignIn`	eq	`high` transforms: `cased`
`SessionId`	is_not_null	(no value, null check)
`TotalCount`	ge	`3` transforms: `cased`
`UserId`	is_not_null	(no value, null check)

Output fields

Fields the rule emits when it matches. Chronicle authors list these in the outcome block; they appear on the detection and $risk_score drives alerting. Sentinel / Defender XDR rules build them up through project / summarize / extend stages. Sentinel maps these into alert fields via entityMappings and customDetails; Defender XDR custom detections surface them as alert fields directly.

Field	Source
`AccountDisplayName`	`project`
`ApplicationId`	`project`
`ReportId`	`project`
`Timestamp`	`project`
`TotalCount`	`project`
`UserId`	`project`
`NTDomain`	`extend`
`Name`	`extend`

`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)

Unusual Volume of file deletion by users

MITRE ATT&CK coverage

Rule body kusto

Stages and Predicates

Parameters

Let binding: `relevantOperations`

Let binding: `riskyUsers`

Stage 1: `source`

Stage 2: `where`

Stage 3: `where`

Stage 4: `where`

Stage 5: `where`

Stage 6: `where`

Stage 7: `where`

Stage 8: `extend`

Stage 9: `where`

Stage 10: `project`

Stage 11: `join`

Stage 12: `summarize`

Stage 13: `summarize`

Stage 14: `where`

Stage 15: `project`

Stage 16: `extend`

Indicators

Output fields

Keyboard shortcuts

Search operators

Unusual Volume of file deletion by users

MITRE ATT&CK coverage

Rule body kusto

Stages and Predicates

Parameters

Let binding: relevantOperations

Let binding: riskyUsers

Stage 1: source

Stage 2: where

Stage 3: where

Stage 4: where

Stage 5: where

Stage 6: where

Stage 7: where

Stage 8: extend

Stage 9: where

Stage 10: project

Stage 11: join

Stage 12: summarize

Stage 13: summarize

Stage 14: where

Stage 15: project

Stage 16: extend

Indicators

Output fields

Let binding: `relevantOperations`

Let binding: `riskyUsers`

Stage 1: `source`

Stage 2: `where`

Stage 3: `where`

Stage 4: `where`

Stage 5: `where`

Stage 6: `where`

Stage 7: `where`

Stage 8: `extend`

Stage 9: `where`

Stage 10: `project`

Stage 11: `join`

Stage 12: `summarize`

Stage 13: `summarize`

Stage 14: `where`

Stage 15: `project`

Stage 16: `extend`