Home/CVE-2021-25376/Sigma rules
Sigma

Sigma rules for CVE-2021-25376

6 rules · scoped to cve · back to CVE-2021-25376
Direct rules mention this entity in their title or description. Related rules cover the techniques this entity is known to use.

Detection rules

6 of 6
direct high
Email Exifiltration Via Powershell
Detects email exfiltration via powershell cmdlets
status test author Nasreddine Bencherchali (Nextron Systems), Azure-Sentinel (idea) id 312d0384-401c-4b8b-abdf-685ffba9a332 license Sigma · DRL-1.1
view Sigma YAML
title: Email Exifiltration Via Powershell
id: 312d0384-401c-4b8b-abdf-685ffba9a332
status: test
description: Detects email exfiltration via powershell cmdlets
references:
    - https://www.microsoft.com/security/blog/2022/09/07/profiling-dev-0270-phosphorus-ransomware-operations/
    - https://github.com/Azure/Azure-Sentinel/blob/7e6aa438e254d468feec061618a7877aa528ee9f/Hunting%20Queries/Microsoft%20365%20Defender/Ransomware/DEV-0270/Email%20data%20exfiltration%20via%20PowerShell.yaml
author: Nasreddine Bencherchali (Nextron Systems),  Azure-Sentinel (idea)
date: 2022-09-09
tags:
    - attack.exfiltration
logsource:
    category: process_creation
    product: windows
detection:
    selection:
        Image|endswith:
            - '\powershell.exe'
            - '\pwsh.exe'
        CommandLine|contains|all:
            - 'Add-PSSnapin'
            - 'Get-Recipient'
            - '-ExpandProperty'
            - 'EmailAddresses'
            - 'SmtpAddress'
            - '-hidetableheaders'
    condition: selection
falsepositives:
    - Unknown
level: high
direct high
Password Protected ZIP File Opened (Email Attachment)
Detects the extraction of password protected ZIP archives. See the filename variable for more details on which file has been opened.
status test author Florian Roth (Nextron Systems) id 571498c8-908e-40b4-910b-d2369159a3da license Sigma · DRL-1.1
view Sigma YAML
title: Password Protected ZIP File Opened (Email Attachment)
id: 571498c8-908e-40b4-910b-d2369159a3da
status: test
description: Detects the extraction of password protected ZIP archives. See the filename variable for more details on which file has been opened.
references:
    - https://twitter.com/sbousseaden/status/1523383197513379841
author: Florian Roth (Nextron Systems)
date: 2022-05-09
tags:
    - attack.initial-access
    - attack.stealth
    - attack.t1027
    - attack.t1566.001
logsource:
    product: windows
    service: security
detection:
    selection:
        EventID: 5379
        TargetName|contains|all:
            - 'Microsoft_Windows_Shell_ZipFolder:filename'
            - '\Temporary Internet Files\Content.Outlook'
    condition: selection
falsepositives:
    - Legitimate used of encrypted ZIP files
level: high
direct medium
Microsoft 365 - User Restricted from Sending Email
Detects when a Security Compliance Center reported a user who exceeded sending limits of the service policies and because of this has been restricted from sending email.
status test author austinsonger id ff246f56-7f24-402a-baca-b86540e3925c license Sigma · DRL-1.1
view Sigma YAML
title: Microsoft 365 - User Restricted from Sending Email
id: ff246f56-7f24-402a-baca-b86540e3925c
status: test
description: Detects when a Security Compliance Center reported a user who exceeded sending limits of the service policies and because of this has been restricted from sending email.
references:
    - https://learn.microsoft.com/en-us/defender-cloud-apps/anomaly-detection-policy
    - https://learn.microsoft.com/en-us/defender-cloud-apps/policy-template-reference
author: austinsonger
date: 2021-08-19
modified: 2022-10-09
tags:
    - attack.initial-access
    - attack.t1199
logsource:
    service: threat_management
    product: m365
detection:
    selection:
        eventSource: SecurityComplianceCenter
        eventName: 'User restricted from sending email'
        status: success
    condition: selection
falsepositives:
    - Unknown
level: medium
direct medium
Suspicious Email Delivered In Microsoft 365
Detects instances where an email, identified as malicious or suspicious by the Microsoft Defender for Office 365 (formerly ATP) engine, was delivered to a user's Inbox or Junk folder. It might indicate that a potential threat, such as a spearphishing attachment or links, has bypassed initial blocking mechanisms and reached an end-user, requiring further investigation and potential remediation.
status experimental author Marco Pedrinazzi (@pedrinazziM) (InTheCyber) id 3569aefd-e535-4391-8c18-24bd01a21eaf license Sigma · DRL-1.1
view Sigma YAML
title: Suspicious Email Delivered In Microsoft 365
id: 3569aefd-e535-4391-8c18-24bd01a21eaf
status: experimental
description: |
    Detects instances where an email, identified as malicious or suspicious by the Microsoft Defender for Office 365 (formerly ATP) engine, was delivered to a user's Inbox or Junk folder.
    It might indicate that a potential threat, such as a spearphishing attachment or links, has bypassed initial blocking mechanisms and reached an end-user, requiring further investigation and potential remediation.
references:
    - https://learn.microsoft.com/en-us/defender-office-365/threat-explorer-real-time-detections-about
    - https://research.splunk.com/cloud/605cc93a-70e4-4ee3-9a3d-1a62e8c9b6c2/
    - https://github.com/Bert-JanP/Hunting-Queries-Detection-Rules/blob/e7250648cb16d4a497ae8737943bf010ea96d2e6/Defender%20For%20Cloud%20Apps/MaliciousEmailDeliveredInMailbox.md
author: Marco Pedrinazzi (@pedrinazziM) (InTheCyber)
date: 2026-01-27
tags:
    - attack.initial-access
    - attack.t1566.001
    - attack.t1566.002
logsource:
    service: audit
    product: m365
detection:
    selection:
        Workload: 'ThreatIntelligence'
        Operation: 'TIMailData'
        Directionality: 'Inbound'
    filter_main_blocked:
        DeliveryAction: 'Blocked'
    condition: selection and not 1 of filter_main_*
falsepositives:
    - Unlikely
level: medium
direct medium
Google Workspace Out Of Domain Email Forwarding
Detects automatic email forwarding to external domains in Google Workspace, which may indicate data leakage or misuse.
status experimental author Tom kluter id 2a0bb2dd-eb5f-4517-8cb9-404f8ba764a5 license Sigma · DRL-1.1
view Sigma YAML
title: Google Workspace Out Of Domain Email Forwarding
id: 2a0bb2dd-eb5f-4517-8cb9-404f8ba764a5
status: experimental
description: Detects automatic email forwarding to external domains in Google Workspace, which may indicate data leakage or misuse.
references:
    - https://developers.google.com/workspace/admin/reports/v1/appendix/activity/login#email_forwarding_out_of_domain
author: Tom kluter
date: 2026-04-28
tags:
    - attack.t1114.003
    - attack.collection
logsource:
    product: gcp
    service: google_workspace.login
detection:
    selection:
        protoPayload.serviceName: 'login.googleapis.com'
        protoPayload.metadata.event.eventName: 'email_forwarding_out_of_domain'
    condition: selection
falsepositives:
    - Legitimate forwarding
level: medium
direct medium
Powershell Local Email Collection
Adversaries may target user email on local systems to collect sensitive information. Files containing email data can be acquired from a users local system, such as Outlook storage or cache files.
status test author frack113 id 2837e152-93c8-43d2-85ba-c3cd3c2ae614 license Sigma · DRL-1.1
view Sigma YAML
title: Powershell Local Email Collection
id: 2837e152-93c8-43d2-85ba-c3cd3c2ae614
status: test
description: |
    Adversaries may target user email on local systems to collect sensitive information.
    Files containing email data can be acquired from a users local system, such as Outlook storage or cache files.
references:
    - https://github.com/redcanaryco/atomic-red-team/blob/f339e7da7d05f6057fdfcdd3742bfcf365fee2a9/atomics/T1114.001/T1114.001.md
author: frack113
date: 2021-07-21
modified: 2022-12-25
tags:
    - attack.collection
    - attack.t1114.001
logsource:
    product: windows
    category: ps_script
    definition: 'Requirements: Script Block Logging must be enabled'
detection:
    selection:
        ScriptBlockText|contains:
            - 'Get-Inbox.ps1'
            - 'Microsoft.Office.Interop.Outlook'
            - 'Microsoft.Office.Interop.Outlook.olDefaultFolders'
            - '-comobject outlook.application'
    condition: selection
falsepositives:
    - Unknown
level: medium
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