title: Suspicious File Created in Outlook Temporary Directory
id: fabb0e80-030c-4e3e-a104-d09676991ac3
related:
    - id: f748c45a-f8d3-4e6f-b617-fe176f695b8f
      type: obsolete
status: experimental
description: |
    Detects the creation of files with suspicious file extensions in the temporary directory that Outlook uses when opening attachments.
    This can be used to detect spear-phishing campaigns that use suspicious files as attachments, which may contain malicious code.
references:
    - https://vipre.com/blog/svg-phishing-attacks-the-new-trick-in-the-cybercriminals-playbook/
    - https://thecyberexpress.com/rogue-rdp-files-used-in-ukraine-cyberattacks/
    - https://www.microsoft.com/en-us/security/blog/2024/10/29/midnight-blizzard-conducts-large-scale-spear-phishing-campaign-using-rdp-files/
author: Florian Roth (Nextron Systems), Swachchhanda Shrawan Poudel (Nextron Systems)
date: 2025-07-22
tags:
    - attack.initial-access
    - attack.t1566.001
logsource:
    product: windows
    category: file_event
detection:
    selection_extension:
        TargetFilename|endswith:
            - '.cpl'
            - '.hta'
            - '.iso'
            - '.rdp'
            - '.svg'
            - '.vba'
            - '.vbe'
            - '.vbs'
    selection_location:
        - TargetFilename|contains:
              - '\AppData\Local\Packages\Microsoft.Outlook_'
              - '\AppData\Local\Microsoft\Olk\Attachments\'
        - TargetFilename|contains|all:
              - '\AppData\Local\Microsoft\Windows\'
              - '\Content.Outlook\'
    condition: all of selection_*
falsepositives:
    - Opening of headers or footers in email signatures that include SVG images or legitimate SVG attachments
level: high

title: Suspicious Outlook Macro Created
id: 117d3d3a-755c-4a61-b23e-9171146d094c
related:
    - id: 8c31f563-f9a7-450c-bfa8-35f8f32f1f61
      type: derived
status: test
description: Detects the creation of a macro file for Outlook.
references:
    - https://www.mdsec.co.uk/2020/11/a-fresh-outlook-on-mail-based-persistence/
    - https://speakerdeck.com/heirhabarov/hunting-for-persistence-via-microsoft-exchange-server-or-outlook?slide=53
    - https://www.linkedin.com/pulse/outlook-backdoor-using-vba-samir-b-/
author: Nasreddine Bencherchali (Nextron Systems)
date: 2023-02-08
tags:
    - attack.privilege-escalation
    - attack.persistence
    - attack.command-and-control
    - attack.t1137
    - attack.t1008
    - attack.t1546
logsource:
    category: file_event
    product: windows
detection:
    selection:
        TargetFilename|endswith: '\Microsoft\Outlook\VbaProject.OTM'
    filter:
        Image|endswith: '\outlook.exe'
    condition: selection and not filter
falsepositives:
    - Unlikely
level: high

title: Potential Persistence Via Outlook Form
id: c3edc6a5-d9d4-48d8-930e-aab518390917
status: test
description: Detects the creation of a new Outlook form which can contain malicious code
references:
    - https://speakerdeck.com/heirhabarov/hunting-for-persistence-via-microsoft-exchange-server-or-outlook?slide=76
    - https://speakerdeck.com/heirhabarov/hunting-for-persistence-via-microsoft-exchange-server-or-outlook?slide=79
    - https://learn.microsoft.com/en-us/office/vba/outlook/concepts/outlook-forms/create-an-outlook-form
    - https://www.slipstick.com/developer/custom-form/clean-outlooks-forms-cache/
author: Tobias Michalski (Nextron Systems)
date: 2021-06-10
modified: 2023-02-22
tags:
    - attack.persistence
    - attack.t1137.003
logsource:
    product: windows
    category: file_event
detection:
    selection:
        Image|endswith: '\outlook.exe'
        TargetFilename|contains:
            - '\AppData\Local\Microsoft\FORMS\IPM'
            - '\Local Settings\Application Data\Microsoft\Forms' # Windows XP
    condition: selection
falsepositives:
    - Legitimate use of outlook forms
level: high

title: Suspicious Execution From Outlook Temporary Folder
id: a018fdc3-46a3-44e5-9afb-2cd4af1d4b39
status: test
description: Detects a suspicious program execution in Outlook temp folder
author: Florian Roth (Nextron Systems)
references:
    - Internal Research
date: 2019-10-01
modified: 2022-10-09
tags:
    - attack.initial-access
    - attack.t1566.001
logsource:
    category: process_creation
    product: windows
detection:
    selection:
        Image|contains: '\Temporary Internet Files\Content.Outlook\'
    condition: selection
falsepositives:
    - Unknown
level: high

title: Suspicious Remote Child Process From Outlook
id: e212d415-0e93-435f-9e1a-f29005bb4723
related:
    - id: 208748f7-881d-47ac-a29c-07ea84bf691d # Outlook Child Processes
      type: similar
status: test
description: Detects a suspicious child process spawning from Outlook where the image is located in a remote location (SMB/WebDav shares).
references:
    - https://github.com/sensepost/ruler
    - https://www.fireeye.com/blog/threat-research/2018/12/overruled-containing-a-potentially-destructive-adversary.html
    - https://speakerdeck.com/heirhabarov/hunting-for-persistence-via-microsoft-exchange-server-or-outlook?slide=49
author: Markus Neis, Nasreddine Bencherchali (Nextron Systems)
date: 2018-12-27
modified: 2023-02-09
tags:
    - attack.execution
    - attack.stealth
    - attack.t1059
    - attack.t1202
logsource:
    category: process_creation
    product: windows
detection:
    selection:
        ParentImage|endswith: '\outlook.exe'
        Image|startswith: '\\\\'
    condition: selection
falsepositives:
    - Unknown
level: high

title: Suspicious Outlook Child Process
id: 208748f7-881d-47ac-a29c-07ea84bf691d
related:
    - id: 438025f9-5856-4663-83f7-52f878a70a50 # Office Child Processes
      type: derived
    - id: e212d415-0e93-435f-9e1a-f29005bb4723 # Outlook Remote Child Process
      type: derived
status: test
description: Detects a suspicious process spawning from an Outlook process.
references:
    - https://www.hybrid-analysis.com/sample/465aabe132ccb949e75b8ab9c5bda36d80cf2fd503d52b8bad54e295f28bbc21?environmentId=100
    - https://mgreen27.github.io/posts/2018/04/02/DownloadCradle.html
author: Michael Haag, Florian Roth (Nextron Systems), Markus Neis, Elastic, FPT.EagleEye Team
date: 2022-02-28
modified: 2023-02-04
tags:
    - attack.execution
    - attack.t1204.002
logsource:
    category: process_creation
    product: windows
detection:
    selection:
        ParentImage|endswith: '\OUTLOOK.EXE'
        Image|endswith:
            - '\AppVLP.exe'
            - '\bash.exe'
            - '\cmd.exe'
            - '\cscript.exe'
            - '\forfiles.exe'
            - '\hh.exe'
            - '\mftrace.exe'
            - '\msbuild.exe'        # https://github.com/elastic/detection-rules/blob/c76a39796972ecde44cb1da6df47f1b6562c9770/rules/windows/defense_evasion_execution_msbuild_started_by_office_app.toml
            - '\msdt.exe'           # CVE-2022-30190
            - '\mshta.exe'
            - '\msiexec.exe'
            - '\powershell.exe'
            - '\pwsh.exe'
            - '\regsvr32.exe'
            - '\schtasks.exe'
            - '\scrcons.exe'
            - '\scriptrunner.exe'
            - '\sh.exe'
            - '\svchost.exe'        # https://www.vmray.com/analyses/2d2fa29185ad/report/overview.html
            - '\wmic.exe'           # https://app.any.run/tasks/c903e9c8-0350-440c-8688-3881b556b8e0/
            - '\wscript.exe'
            # Several FPs with rundll32.exe
            # We started excluding specific use cases and ended up commenting out the rundll32.exe sub processes completely
            # - '\rundll32.exe'
            # filter_outlook_photoviewer:  # https://twitter.com/Luke_Hamp/status/1495919717760237568
            #   ParentImage|endswith: '\OUTLOOK.EXE'
            #   Image|endswith: '\rundll32.exe'
            #   CommandLine|contains: '\PhotoViewer.dll'
            # filter_outlook_printattachments:  # https://twitter.com/KickaKamil/status/1496238278659485696
            #   ParentImage|endswith: '\OUTLOOK.EXE'
            #   Image|endswith: '\rundll32.exe'
            #   CommandLine|contains|all:
            #     - 'shell32.dll,Control_RunDLL'
            #     - '\SYSTEM32\SPOOL\DRIVERS\'
    condition: selection # and not 1 of filter*
falsepositives:
    - Unknown
level: high

title: Outlook EnableUnsafeClientMailRules Setting Enabled
id: 55f0a3a1-846e-40eb-8273-677371b8d912
related:
    - id: 6763c6c8-bd01-4687-bc8d-4fa52cf8ba08 # Registry variation
      type: similar
status: test
description: Detects an attacker trying to enable the outlook security setting "EnableUnsafeClientMailRules" which allows outlook to run applications or execute macros
references:
    - https://www.fireeye.com/blog/threat-research/2018/12/overruled-containing-a-potentially-destructive-adversary.html
    - https://speakerdeck.com/heirhabarov/hunting-for-persistence-via-microsoft-exchange-server-or-outlook?slide=44
    - https://support.microsoft.com/en-us/topic/how-to-control-the-rule-actions-to-start-an-application-or-run-a-macro-in-outlook-2016-and-outlook-2013-e4964b72-173c-959d-5d7b-ead562979048
author: Markus Neis, Nasreddine Bencherchali (Nextron Systems)
date: 2018-12-27
modified: 2023-02-09
tags:
    - attack.execution
    - attack.stealth
    - attack.t1059
    - attack.t1202
logsource:
    category: process_creation
    product: windows
detection:
    selection:
        CommandLine|contains: '\Outlook\Security\EnableUnsafeClientMailRules'
    condition: selection
falsepositives:
    - Unknown
level: high

title: Potential Persistence Via Outlook LoadMacroProviderOnBoot Setting
id: 396ae3eb-4174-4b9b-880e-dc0364d78a19
status: test
description: Detects the modification of Outlook setting "LoadMacroProviderOnBoot" which if enabled allows the automatic loading of any configured VBA project/module
references:
    - https://speakerdeck.com/heirhabarov/hunting-for-persistence-via-microsoft-exchange-server-or-outlook?slide=53
    - https://www.linkedin.com/pulse/outlook-backdoor-using-vba-samir-b-/
author: Nasreddine Bencherchali (Nextron Systems)
date: 2021-04-05
modified: 2023-08-17
tags:
    - attack.privilege-escalation
    - attack.persistence
    - attack.command-and-control
    - attack.t1137
    - attack.t1008
    - attack.t1546
logsource:
    category: registry_set
    product: windows
detection:
    selection:
        TargetObject|endswith: '\Outlook\LoadMacroProviderOnBoot'
        Details|contains: '0x00000001'
    condition: selection
falsepositives:
    - Unknown
level: high

title: Potential Persistence Via Outlook Today Page
id: 487bb375-12ef-41f6-baae-c6a1572b4dd1
related:
    - id: ddd171b5-2cc6-4975-9e78-f0eccd08cc76
      type: similar
status: test
description: |
    Detects potential persistence activity via outlook today page.
    An attacker can set a custom page to execute arbitrary code and link to it via the registry values "URL" and "UserDefinedUrl".
references:
    - https://speakerdeck.com/heirhabarov/hunting-for-persistence-via-microsoft-exchange-server-or-outlook?slide=74
    - https://trustedsec.com/blog/specula-turning-outlook-into-a-c2-with-one-registry-change
author: Tobias Michalski (Nextron Systems), David Bertho (@dbertho) & Eirik Sveen (@0xSV1), Storebrand
date: 2021-06-10
modified: 2024-08-07
tags:
    - attack.persistence
    - attack.defense-impairment
    - attack.t1112
logsource:
    product: windows
    category: registry_set
detection:
    selection_main:
        TargetObject|contains|all:
            - 'Software\Microsoft\Office\'
            - '\Outlook\Today\'
    selection_value_stamp:
        TargetObject|endswith: '\Stamp'
        Details: 'DWORD (0x00000001)'
    selection_value_url:
        TargetObject|endswith:
            - '\URL'
            - '\UserDefinedUrl'
    filter_main_office:
        Image|startswith:
            - 'C:\Program Files\Common Files\Microsoft Shared\ClickToRun\'
            - 'C:\Program Files\Common Files\Microsoft Shared\ClickToRun\Updates\'
        Image|endswith: '\OfficeClickToRun.exe'
    condition: selection_main and 1 of selection_value_* and not 1 of filter_main_*
falsepositives:
    - Unknown
level: high

title: Potential Persistence Via Outlook Home Page
id: ddd171b5-2cc6-4975-9e78-f0eccd08cc76
related:
    - id: 487bb375-12ef-41f6-baae-c6a1572b4dd1
      type: similar
status: test
description: |
    Detects potential persistence activity via outlook home page.
    An attacker can set a home page to achieve code execution and persistence by editing the WebView registry keys.
references:
    - https://speakerdeck.com/heirhabarov/hunting-for-persistence-via-microsoft-exchange-server-or-outlook?slide=70
    - https://support.microsoft.com/en-us/topic/outlook-home-page-feature-is-missing-in-folder-properties-d207edb7-aa02-46c5-b608-5d9dbed9bd04?ui=en-us&rs=en-us&ad=us
    - https://trustedsec.com/blog/specula-turning-outlook-into-a-c2-with-one-registry-change
author: Tobias Michalski (Nextron Systems), David Bertho (@dbertho) & Eirik Sveen (@0xSV1), Storebrand
date: 2021-06-09
modified: 2024-08-07
tags:
    - attack.persistence
    - attack.defense-impairment
    - attack.t1112
logsource:
    product: windows
    category: registry_set
detection:
    selection:
        TargetObject|contains|all:
            - '\Software\Microsoft\Office\'
            - '\Outlook\WebView\'
        TargetObject|endswith: '\URL'
    condition: selection
falsepositives:
    - Unknown
level: high

title: Outlook Macro Execution Without Warning Setting Enabled
id: e3b50fa5-3c3f-444e-937b-0a99d33731cd
status: test
description: Detects the modification of Outlook security setting to allow unprompted execution of macros.
references:
    - https://www.mdsec.co.uk/2020/11/a-fresh-outlook-on-mail-based-persistence/
    - https://speakerdeck.com/heirhabarov/hunting-for-persistence-via-microsoft-exchange-server-or-outlook?slide=53
author: '@ScoubiMtl'
date: 2021-04-05
modified: 2023-08-17
tags:
    - attack.privilege-escalation
    - attack.persistence
    - attack.command-and-control
    - attack.t1137
    - attack.t1008
    - attack.t1546
logsource:
    category: registry_set
    product: windows
detection:
    selection:
        TargetObject|endswith: '\Outlook\Security\Level'
        Details|contains: '0x00000001' # Enable all Macros
    condition: selection
falsepositives:
    - Unlikely
level: high

title: Outlook EnableUnsafeClientMailRules Setting Enabled - Registry
id: 6763c6c8-bd01-4687-bc8d-4fa52cf8ba08
related:
    - id: c3cefdf4-6703-4e1c-bad8-bf422fc5015a
      type: similar
    - id: 55f0a3a1-846e-40eb-8273-677371b8d912 # ProcCreation variation
      type: similar
status: test
description: Detects an attacker trying to enable the outlook security setting "EnableUnsafeClientMailRules" which allows outlook to run applications or execute macros
references:
    - https://support.microsoft.com/en-us/topic/how-to-control-the-rule-actions-to-start-an-application-or-run-a-macro-in-outlook-2016-and-outlook-2013-e4964b72-173c-959d-5d7b-ead562979048
    - https://speakerdeck.com/heirhabarov/hunting-for-persistence-via-microsoft-exchange-server-or-outlook?slide=44
author: Nasreddine Bencherchali (Nextron Systems)
date: 2023-02-08
modified: 2023-08-17
tags:
    - attack.persistence
    - attack.defense-impairment
    - attack.t1112
logsource:
    category: registry_set
    product: windows
detection:
    selection:
        TargetObject|endswith: '\Outlook\Security\EnableUnsafeClientMailRules'
        Details: 'DWORD (0x00000001)'
    condition: selection
falsepositives:
    - Unknown
level: high

title: New Outlook Macro Created
id: 8c31f563-f9a7-450c-bfa8-35f8f32f1f61
related:
    - id: 117d3d3a-755c-4a61-b23e-9171146d094c
      type: derived
status: test
description: Detects the creation of a macro file for Outlook.
references:
    - https://www.mdsec.co.uk/2020/11/a-fresh-outlook-on-mail-based-persistence/
author: '@ScoubiMtl'
date: 2021-04-05
modified: 2023-02-08
tags:
    - attack.privilege-escalation
    - attack.persistence
    - attack.command-and-control
    - attack.t1137
    - attack.t1008
    - attack.t1546
logsource:
    category: file_event
    product: windows
detection:
    selection:
        Image|endswith: '\outlook.exe'
        TargetFilename|endswith: '\Microsoft\Outlook\VbaProject.OTM'
    condition: selection
falsepositives:
    - User genuinely creates a VB Macro for their email
level: medium

title: Microsoft VBA For Outlook Addin Loaded Via Outlook
id: 9a0b8719-cd3c-4f0a-90de-765a4cb3f5ed
status: test
description: Detects outlvba (Microsoft VBA for Outlook Addin) DLL being loaded by the outlook process
references:
    - https://speakerdeck.com/heirhabarov/hunting-for-persistence-via-microsoft-exchange-server-or-outlook?slide=58
author: Nasreddine Bencherchali (Nextron Systems)
date: 2023-02-08
modified: 2024-03-12
tags:
    - attack.execution
    - attack.t1204.002
logsource:
    category: image_load
    product: windows
detection:
    selection:
        Image|endswith: '\outlook.exe'
        ImageLoaded|endswith: '\outlvba.dll'
    condition: selection
falsepositives:
    - Legitimate macro usage. Add the appropriate filter according to your environment
level: medium

title: Outlook Security Settings Updated - Registry
id: c3cefdf4-6703-4e1c-bad8-bf422fc5015a
related:
    - id: 6763c6c8-bd01-4687-bc8d-4fa52cf8ba08 # EnableUnsafeClientMailRules
      type: similar
status: test
description: Detects changes to the registry values related to outlook security settings
references:
    - https://github.com/redcanaryco/atomic-red-team/blob/f339e7da7d05f6057fdfcdd3742bfcf365fee2a9/atomics/T1137/T1137.md
    - https://learn.microsoft.com/en-us/outlook/troubleshoot/security/information-about-email-security-settings
author: frack113
date: 2021-12-28
modified: 2026-01-09
tags:
    - attack.persistence
    - attack.t1137
logsource:
    category: registry_set
    product: windows
detection:
    selection:
        TargetObject|contains|all:
            - '\SOFTWARE\Microsoft\Office\'
            - '\Outlook\Security\'
    filter_main_outlook:
        Image|startswith:
            - 'C:\Program Files\Microsoft Office\'
            - 'C:\Program Files (x86)\Microsoft Office\'
        Image|endswith: '\OUTLOOK.EXE'
    condition: selection and not 1 of filter_main_*
falsepositives:
    - Administrative activity
level: medium