Microsoft365 External Document Sharing

Severity: low
Log types: Microsoft365.Audit.SharePoint
Reference: https://support.microsoft.com/en-us/topic/manage-sharing-with-external-users-in-microsoft-365-small-business-2951a85f-c970-4375-aa4f-6b0d7035fe35#:~:text=Top%20of%20Page-,Turn%20external%20sharing%20on%20or%20off,-The%20ability%20to
Source: github.com/panther-labs/panther-analysis

Document shared externally

MITRE ATT&CK coverage

Tactic	Techniques
Collection	`T1039` Data from Network Shared Drive

Rule body yaml

AnalysisType: rule
Description: Document shared externally
DisplayName: "Microsoft365 External Document Sharing"
Enabled: true
Filename: microsoft365_external_sharing.py
Reports:
  MITRE ATT&CK:
    - TA0009:T1039 # Collection - Data from Network Shared Drive
Runbook: Check the document metadata to ensure it is not a sensitive document.
Reference: https://support.microsoft.com/en-us/topic/manage-sharing-with-external-users-in-microsoft-365-small-business-2951a85f-c970-4375-aa4f-6b0d7035fe35#:~:text=Top%20of%20Page-,Turn%20external%20sharing%20on%20or%20off,-The%20ability%20to
Severity: Low
Tests:
  - ExpectedResult: false
    Log:
      AppAccessContext:
        AADSessionId: aa-bb-cc
        CorrelationId: dd-ee-ff
      ClientIP: 1.2.3.4
      CreationTime: "2022-12-12 19:31:41"
      EventData: <Type>Edit</Type><MembersCanShareApplied>False</MembersCanShareApplied>
      EventSource: SharePoint
      Id: 111-aa-234
      ItemType: File
      ObjectId: https://yourorg.sharepoint.com/personal/user_yourorg/Documents/importantsecrets.docx
      Operation: AddedToSecureLink
      OrganizationId: 11-22-abc
      RecordType: 14
      Site: aa-bb-dd-ee-ff
      SiteUrl: https://yourorg.sharepoint.com/personal/user_yourorg
      SourceFileExtension: docx
      SourceFileName: importantsecrets.docx
      SourceRelativeUrl: Documents/importantsecrets.docx
      TargetUserOrGroupName: OUTSIDER@ALLOWEDDOMAIN.COM
      TargetUserOrGroupType: Guest
      UserAgent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10_15_7) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/108.0.0.0 Safari/537.36
      UserId: my.user@yourorg.onmicrosoft.com
      UserKey: i:0h.f|membership|12345@live.com
      UserType: 0
      Workload: OneDrive
    Name: Allowed Domain
  - ExpectedResult: false
    Log:
      AppAccessContext:
        AADSessionId: aa-bb-cc
        CorrelationId: dd-ee-ff
      ClientIP: 1.2.3.4
      CreationTime: "2022-12-12 19:31:41"
      EventData: <Type>Edit</Type><MembersCanShareApplied>False</MembersCanShareApplied>
      EventSource: SharePoint
      Id: 111-aa-234
      ItemType: File
      ObjectId: https://yourorg.sharepoint.com/personal/user_yourorg/Documents/External/public.docx
      Operation: AddedToSecureLink
      OrganizationId: 11-22-abc
      RecordType: 14
      Site: aa-bb-dd-ee-ff
      SiteUrl: https://yourorg.sharepoint.com/personal/user_yourorg
      SourceFileExtension: docx
      SourceFileName: public.docx
      SourceRelativeUrl: Documents/External/public.docx
      TargetUserOrGroupName: MARKETING@SAAS.COM
      TargetUserOrGroupType: Guest
      UserAgent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10_15_7) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/108.0.0.0 Safari/537.36
      UserId: my.user@yourorg.onmicrosoft.com
      UserKey: i:0h.f|membership|12345@live.com
      UserType: 0
      Workload: OneDrive
    Name: Allowed Folder
  - ExpectedResult: false
    Log:
      AppAccessContext:
        AADSessionId: aa-bb-cc
        CorrelationId: dd-ee-ff
      ClientIP: 1.2.3.4
      CreationTime: "2022-12-12 19:31:41"
      EventData: <Type>Edit</Type><MembersCanShareApplied>False</MembersCanShareApplied>
      EventSource: SharePoint
      Id: 111-aa-234
      ItemType: File
      ObjectId: https://yourorg.sharepoint.com/personal/user_yourorg/Documents/importantsecrets.docx
      Operation: AddedToSecureLink
      OrganizationId: 11-22-abc
      RecordType: 14
      Site: aa-bb-dd-ee-ff
      SiteUrl: https://yourorg.sharepoint.com/personal/user_yourorg
      SourceFileExtension: docx
      SourceFileName: importantsecrets.docx
      SourceRelativeUrl: Documents/importantsecrets.docx
      TargetUserOrGroupName: EXCEPTION@OUTSIDER.COM
      TargetUserOrGroupType: Guest
      UserAgent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10_15_7) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/108.0.0.0 Safari/537.36
      UserId: my.user@yourorg.onmicrosoft.com
      UserKey: i:0h.f|membership|12345@live.com
      UserType: 0
      Workload: OneDrive
    Name: Allowed User
  - ExpectedResult: true
    Log:
      AppAccessContext:
        AADSessionId: aa-bb-cc
        CorrelationId: dd-ee-ff
      ClientIP: 1.2.3.4
      CreationTime: "2022-12-12 19:31:41"
      EventData: <Type>Edit</Type><MembersCanShareApplied>False</MembersCanShareApplied>
      EventSource: SharePoint
      Id: 111-aa-234
      ItemType: File
      ObjectId: https://yourorg.sharepoint.com/personal/user_yourorg/Documents/importantsecrets.docx
      Operation: AddedToSecureLink
      OrganizationId: 11-22-abc
      RecordType: 14
      Site: aa-bb-dd-ee-ff
      SiteUrl: https://yourorg.sharepoint.com/personal/user_yourorg
      SourceFileExtension: docx
      SourceFileName: importantsecrets.docx
      SourceRelativeUrl: Documents/importantsecrets.docx
      TargetUserOrGroupName: OUTSIDER@EXTERNAL.IO
      TargetUserOrGroupType: Guest
      UserAgent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10_15_7) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/108.0.0.0 Safari/537.36
      UserId: my.user@yourorg.onmicrosoft.com
      UserKey: i:0h.f|membership|12345@live.com
      UserType: 0
      Workload: OneDrive
    Name: External user
  - ExpectedResult: false
    Log:
      AppAccessContext:
        AADSessionId: aa-bb-cc
        CorrelationId: dd-ee-ff
      ClientIP: 1.2.3.4
      CreationTime: "2022-12-12 19:31:41"
      EventData: <Type>Edit</Type><MembersCanShareApplied>False</MembersCanShareApplied>
      EventSource: SharePoint
      Id: 111-aa-234
      ItemType: File
      ObjectId: https://yourorg.sharepoint.com/personal/user_yourorg/Documents/importantsecrets.docx
      Operation: AddedToSecureLink
      OrganizationId: 11-22-abc
      RecordType: 14
      Site: aa-bb-dd-ee-ff
      SiteUrl: https://yourorg.sharepoint.com/personal/user_yourorg
      SourceFileExtension: docx
      SourceFileName: importantsecrets.docx
      SourceRelativeUrl: Documents/importantsecrets.docx
      TargetUserOrGroupName: ANOTHERUSER@MYCOMPANY.COM
      TargetUserOrGroupType: NotGuest
      UserAgent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10_15_7) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/108.0.0.0 Safari/537.36
      UserId: my.user@yourorg.onmicrosoft.com
      UserKey: i:0h.f|membership|12345@live.com
      UserType: 0
      Workload: OneDrive
    Name: Internal Share
DedupPeriodMinutes: 60
LogTypes:
  - Microsoft365.Audit.SharePoint
RuleID: "Microsoft365.External.Document.Sharing"
Threshold: 1

Detection logic

Condition

(Operation eq "AnonymousLinkCreated" and not (SourceRelativeUrl wildcard "*/External/*" or SourceRelativeUrl wildcard "External/*")) or (Operation eq "AddedToSecureLink" and not (SourceRelativeUrl wildcard "*/External/*" or SourceRelativeUrl wildcard "External/*") and TargetUserOrGroupName not in "exception@outsider.com")

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
`Operation`	eq	`AddedToSecureLink` `AnonymousLinkCreated`

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
`operation`	`Operation`
`organization_id`	`OrganizationId`
`client_ip`	`ClientIp`
`extended_properties`	`ExtendedProperties`
`modified_properties`	`ModifiedProperties`
`application`	`Application`
`actor`	`Actor`
`SourceRelativeUrl`
`UserId`

`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)