Level 2 file extensions must be blocked and not removed.
Overview
| Finding ID | Version | Rule ID | IA Controls | Severity |
| V-228442 | DTOO245 | SV-228442r508021_rule | CCI-001662 | medium |
| Description | ||||
| This policy setting controls which types of attachments (determined by file extension) must be saved to disk before users can open them. Files with specific extensions can be categorized as Level 1 (users cannot view the file) or Level 2 (users can open the file after saving it to disk). Users can freely open files of types that are not categorized as Level 1 or Level 2. If you enable this policy setting, you can specify a list of attachment file types to classify as Level 2, which forces users to actively decide to download the attachment to view it. If you disable or do not configure this policy setting, Outlook does not classify any file type extensions as Level 2. Important: This policy setting only applies if the "Outlook Security Mode" policy setting under "Microsoft Outlook 2016\Security\Security Form Settings" is configured to "Use Outlook Security Group Policy." | ||||
| STIG | Date | |||
| Microsoft Outlook 2016 Security Technical Implementation Guide | 2022-03-11 | |||
Related Frameworks
1 mapping across 4 frameworks
Related Frameworks
SCF0 mappings
No source states a mapping between these directly.
Also reachable in 3 hops (3) derived by us, not asserted by any source
Each of these is a route we composed by chaining published mappings. No publisher states a relationship between the two endpoints.
- DISA STIG Benchmark (XCCDF)2intersects(normalised)
- DISA CCI List2025-01-23equal to(normalised)
- SCF Secure Traceability Relationship Mapping (STRM)2026.2intersects
- DISA STIG Benchmark (XCCDF)2intersects(normalised)
- DISA CCI List2025-01-23equal to(normalised)
- SCF Secure Traceability Relationship Mapping (STRM)2026.2intersects
- DISA STIG Benchmark (XCCDF)2intersects(normalised)
- DISA CCI List2025-01-23equal to(normalised)
- SCF Secure Traceability Relationship Mapping (STRM)2026.2intersects
NIST 800-530 mappings
No source states a mapping between these directly.
Also reachable in 2 hops (4) derived by us, not asserted by any source
Each of these is a route we composed by chaining published mappings. No publisher states a relationship between the two endpoints.
- DISA STIG Benchmark (XCCDF)2intersects(normalised)
- DISA STIG Benchmark (XCCDF)3our copyintersects(normalised)
- DISA STIG Benchmark (XCCDF)3intersects(normalised)
- DISA CCI List2025-01-23equal to(normalised)
- DISA STIG Benchmark (XCCDF)2intersects(normalised)
- DISA CCI List2025-01-23equal to(normalised)
- DISA STIG Benchmark (XCCDF)2intersects(normalised)
- DISA STIG Benchmark (XCCDF)V2R1our copyintersects(normalised)
- DISA STIG Benchmark (XCCDF)V2R1intersects(normalised)
- DISA CCI List2025-01-23equal to(normalised)
- DISA STIG Benchmark (XCCDF)2intersects(normalised)
- DISA STIG Benchmark (XCCDF)V2R1our copyintersects(normalised)
- DISA STIG Benchmark (XCCDF)V2R1intersects(normalised)
- DISA CCI List2025-01-23equal to(normalised)
CCI1 mapping
CCI-001662
1.00
- DISA STIG Benchmark (XCCDF)2intersects(normalised)
NIST CSF 2.00 mappings
No source states a mapping between these directly.
Also reachable in 4 hops (2) derived by us, not asserted by any source
Each of these is a route we composed by chaining published mappings. No publisher states a relationship between the two endpoints.
ID.RA-08
0.50
- DISA STIG Benchmark (XCCDF)2intersects(normalised)
- DISA CCI List2025-01-23equal to(normalised)
- SCF Secure Traceability Relationship Mapping (STRM)2026.2intersects
- NIST OLIR Informative ReferenceOLIR 153 (2025-04-07)intersects(normalised)SCF Focal Document mapping (catalog)SCF 2026.2 focalintersects(normalised)
PR.PS-02
0.50
- DISA STIG Benchmark (XCCDF)2intersects(normalised)
- DISA CCI List2025-01-23equal to(normalised)
- SCF Secure Traceability Relationship Mapping (STRM)2026.2intersects
- NIST OLIR Informative ReferenceOLIR 153 (2025-04-07)intersects(normalised)SCF Focal Document mapping (catalog)SCF 2026.2 focalintersects(normalised)
Details
Check Text (C-228442r508021_chk)
Verify the policy value for User Configuration -> Administrative Templates -> Microsoft Outlook 2016 -> Security -> Security Form Settings -> Attachment Security "Remove file extensions blocked as Level 2" is set to "Disabled".
Procedure: Use the Windows Registry Editor to navigate to the following key:
HKCU\Software\Policies\Microsoft\Office\16.0\outlook\security\FileExtensionsRemoveLevel2
Criteria: If the registry key exists, this is a finding.
Fix Text (F-30660r497649_fix)
Set the policy value for User Configuration -> Administrative Templates -> Microsoft Outlook 2016 -> Security -> Security Form Settings -> Attachment Security "Remove file extensions blocked as Level 2" to "Disabled".