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Detection rules › Splunk

O365 Safe Links Detection

Status
production
Severity
medium
Group by
AlertId, Name, aws::recipientAccountId, dest, ot, src, trc, vendor_product
Author
Steven Dick
Source
github.com/splunk/security_content

The following analytic detects when any Microsoft Safe Links alerting is triggered. This behavior may indicate when user has interacted with a phishing or otherwise malicious link within the Microsoft Office ecosystem.

MITRE ATT&CK coverage

TacticTechniques
Initial AccessT1566.001 Phishing: Spearphishing Attachment

Rule body splunk

name: O365 Safe Links Detection
id: 711d9e8c-2cb0-45cf-8813-5f191ecb9b26
version: 11
creation_date: '2024-04-07'
modification_date: '2026-05-13'
author: Steven Dick
status: production
type: TTP
description: The following analytic detects when any Microsoft Safe Links alerting is triggered. This behavior may indicate when user has interacted with a phishing or otherwise malicious link within the Microsoft Office ecosystem.
data_source:
    - Office 365 Universal Audit Log
search: |-
    `o365_management_activity` Name="*a potentially malicious URL*" Operation=AlertEntityGenerated
      | fromjson Data
      | fillnull
      | stats count min(_time) as firstTime max(_time) as lastTime values(ObjectId) as url values(od) as desc
        BY AlertId, trc, Name,
           ot, dest, vendor_account,
           vendor_product, src
      | rename Name as signature, AlertId as signature_id, trc as user, ot as action
      | eval action = CASE(action == "Allowed", "allowed", action=="BlockPageOverride", "allowed", true(),"blocked")
      | `security_content_ctime(firstTime)`
      | `security_content_ctime(lastTime)`
      | `o365_safe_links_detection_filter`
how_to_implement: You must install the Splunk Microsoft Office 365 Add-on and ingest Office 365 management activity events. The Safe Links capability must be configured and is typically only available to E3/E5 level customers.
known_false_positives: Based on Safe Links policies, may vary.
references:
    - https://learn.microsoft.com/en-us/microsoft-365/security/office-365-security/safe-links-about?view=o365-worldwide
    - https://attack.mitre.org/techniques/T1566/
drilldown_searches:
    - name: View the detection results for - "$user$"
      search: '%original_detection_search% | search  user = "$user$"'
      earliest_offset: $info_min_time$
      latest_offset: $info_max_time$
    - name: View risk events for the last 7 days for - "$user$"
      search: '| from datamodel Risk.All_Risk | search normalized_risk_object IN ("$user$") | stats count min(_time) as firstTime max(_time) as lastTime values(search_name) as "Search Name" values(risk_message) as "Risk Message" values(analyticstories) as "Analytic Stories" values(annotations._all) as "Annotations" values(annotations.mitre_attack.mitre_tactic) as "ATT&CK Tactics" by normalized_risk_object | `security_content_ctime(firstTime)` | `security_content_ctime(lastTime)`'
      earliest_offset: 7d
      latest_offset: "0"
finding:
    title: $user$ triggered a Microsoft Safe Links detection.
    entity:
        field: user
        type: user
        score: 50
analytic_story:
    - Office 365 Account Takeover
    - Spearphishing Attachments
asset_type: O365 Tenant
mitre_attack_id:
    - T1566.001
product:
    - Splunk Enterprise
    - Splunk Enterprise Security
    - Splunk Cloud
category: cloud
security_domain: threat
tests:
    - name: True Positive Test
      attack_data:
        - data: https://media.githubusercontent.com/media/splunk/attack_data/master/datasets/attack_techniques/T1566/o365_various_alerts/o365_various_alerts.log
          sourcetype: o365:management:activity
          source: o365
      test_type: unit

Stages and Predicates

Stage 1: search

`o365_management_activity` Name="*a potentially malicious URL*" Operation=AlertEntityGenerated

Stage 2: search

| fromjson Data

Stage 3: fillnull

| fillnull

Stage 4: stats

| stats count min(_time) as firstTime max(_time) as lastTime values(ObjectId) as url values(od) as desc
    BY AlertId, trc, Name,
       ot, dest, vendor_account,
       vendor_product, src

Stage 5: rename

| rename Name as signature, AlertId as signature_id, trc as user, ot as action

Stage 6: eval

| eval action = CASE(action == "Allowed", "allowed", action=="BlockPageOverride", "allowed", true(),"blocked")
action =
if"allowed"
elif"allowed"
else"blocked"

Stage 7: search

| `security_content_ctime(firstTime)`

Stage 8: search

| `security_content_ctime(lastTime)`

Stage 9: search

| `o365_safe_links_detection_filter`

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.

FieldKindValues
Nameeq
  • "*a potentially malicious URL*"
Operationeq
  • AlertEntityGenerated
sourcetypeeq
  • o365:management:activity

Search terms

Bare-string tokens in the SPL search body. Splunk matches each token against _raw (the untyped raw event text) anywhere it appears, not against a specific field. These don't surface in the Indicators table because they aren't predicates on a known field.

StageTerm
2fromjson
2Data