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Allow or block files using the Tenant Allow/Block List

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  • 8 minutes to read

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Applies to

This article describes how to manage file allow and block entries that are available in the Tenant Allow/Block List. For more information about the Tenant Allow/Block List, see Manage your allows and blocks in the Tenant Allow/Block List.

You manage allow and block entries for files in the Microsoft 365 Defender Portal or in Exchange Online PowerShell.

What do you need to know before you begin?

  • You open the Microsoft 365 Defender portal at https://security.microsoft.com. To go directly to the Tenant Allow/Block List page, use https://security.microsoft.com/tenantAllowBlockList. To go directly to the Submissions page, use https://security.microsoft.com/reportsubmission.

  • To connect to Exchange Online PowerShell, see Connect to Exchange Online PowerShell. To connect to standalone EOP PowerShell, see Connect to Exchange Online Protection PowerShell.

  • You specify files by using the SHA256 hash value of the file. To find the SHA256 hash value of a file in Windows, run the following command in a Command Prompt:

    certutil.exe -hashfile "<Path>\<Filename>" SHA256

    An example value is 768a813668695ef2483b2bde7cf5d1b2db0423a0d3e63e498f3ab6f2eb13ea3a. Perceptual hash (pHash) values are not supported.

  • For files, the maximum number of allow entries is 500, and the maximum number of block entries is 500 (1000 file entries total).

  • You can enter a maximum of 64 characters in a file entry.

  • An entry should be active within 30 minutes, but it might take up to 24 hours for the entry to be active.

  • You need to be assigned permissions in Exchange Online before you can do the procedures in this article:

    • To add and remove values from the Tenant Allow/Block List, you need to be a member of one of the following role groups:
      • Organization Management or Security Administrator role group (Security admin role)
      • Security Operator role group (Tenant AllowBlockList Manager).
    • For read-only access to the Tenant Allow/Block List, you need to be a member of one of the following role groups:
      • Global Reader role group
      • Security Reader role group
      • View-Only configuration role group

    For more information, see Permissions in Exchange Online.

    Notes:

    • Adding users to the corresponding Azure Active Directory role in the Microsoft 365 admin center gives users the required permissions and permissions for other features in Microsoft 365. For more information, see About admin roles.
    • The View-Only Organization Management role group in Exchange Online also gives read-only access to the feature.

Create block entries for files

You have the following options to create block entries for files:

Use the Microsoft 365 Defender portal to create block entries for files in the Submissions portal

When you use the Submissions portal at https://security.microsoft.com/reportsubmission to report files as Should have been blocked (False negative), you can select Block this file to add a block entry on the Files tab in the Tenant Allow/Block List.

For instructions, see Report questionable email attachments to Microsoft.

Use the Microsoft 365 Defender portal to create block entries for files in the Tenant Allow/Block List

You can create block entries for files directly in the Tenant Allow/Block List.

Email messages that contain these blocked files are blocked as malware.

  1. In the Microsoft 365 Defender portal at https://security.microsoft.com, go to Policies & rules > Threat Policies > Rules section > Tenant Allow/Block Lists. Or, to go directly to the Tenant Allow/Block List page, use https://security.microsoft.com/tenantAllowBlockList.

  2. On the Tenant Allow/Block List page, select the Files tab.

  3. On the Files tab, click Block icon. Block.

  4. In the Block files flyout that appears, configure the following settings:

    • Add file hashes: Enter one SHA256 hash value per line, up to a maximum of 20.

    • Remove block entry after: The default value is 30 days, but you can select from the following values:

      • 1 day
      • 7 days
      • 30 days
      • Never expire
      • Specific date: The maximum value is 90 days from today.

    • Optional note: Enter descriptive text for the entries.

  5. When you're finished, click Add.

Use PowerShell to create block entries for files in the Tenant Allow/Block List

In Exchange Online PowerShell, use the following syntax:

New-TenantAllowBlockListItems -ListType <FileHash> -Block -Entries "Value1","Value2",..."ValueN" <-ExpirationDate Date | -NoExpiration> [-Notes <String>]

This example adds a block entry for the specified files that never expires.

New-TenantAllowBlockListItems -ListType FileHash -Block -Entries "768a813668695ef2483b2bde7cf5d1b2db0423a0d3e63e498f3ab6f2eb13ea3","2c0a35409ff0873cfa28b70b8224e9aca2362241c1f0ed6f622fef8d4722fd9a" -NoExpiration

For detailed syntax and parameter information, see New-TenantAllowBlockListItems.

Use the Microsoft 365 Defender portal to create allow entries for files in the Submissions portal

You can't create allow entries for files directly in the Tenant Allow/Block List. Instead, you use the Submissions portal at https://security.microsoft.com/reportsubmission to report the message attachment as a false positive, which also adds an allow entry on the Files tab in the Tenant Allow/Block List.

For instructions, see Report good email attachments to Microsoft.

Important

Because Microsoft manages allow entries for you, unneeded allow entries for files will be removed. This behavior protects your organization and helps prevent misconfigured allow entries. If you disagree with the verdict, you might need to open a support case to help determine why a file is still considered bad.

Use the Microsoft 365 Defender portal to view allow or block entries for files in the Tenant Allow/Block List

  1. In the Microsoft 365 Defender portal at https://security.microsoft.com, go to Policies & rules > Threat Policies > Tenant Allow/Block Lists in the Rules section. Or, to go directly to the Tenant Allow/Block Lists page, use https://security.microsoft.com/tenantAllowBlockList.

  2. Select the Files tab. The following columns are available:

    • Value: The file hash.
    • Action: The value Allow or Block.
    • Modified by
    • Last updated
    • Remove on: The expiration date.
    • Notes

    You can click on a column heading to sort in ascending or descending order.

    Click Group icon. Group to group the results by None or Action.

    Click Search icon. Search, enter all or part of a value, and then press ENTER to find a specific value. When you're finished, click Clear search icon. Clear search.

    Click Filter icon. Filter to filter the results. The following values are available in the Filter flyout that appears:

    • Action: Allow and Block.
    • Never expire: Toggle on. or Toggle off.
    • Last updated: Select From and To dates.
    • Remove on: Select From and To dates.

    When you're finished, click Apply. To clear existing filters, click Clear filters icon Clear filters in the Filter flyout.

Use PowerShell to view allow or block entries for files in the Tenant Allow/Block List

In Exchange Online PowerShell, use the following syntax:

Get-TenantAllowBlockListItems -ListType FileHash [-Allow] [-Block] [-Entry <FileHashValue>] [<-ExpirationDate Date | -NoExpiration>]

This example returns all allowed and blocked files.

Get-TenantAllowBlockListItems -ListType FileHash

This example returns information for the specified file hash value.

Get-TenantAllowBlockListItems -ListType FileHash -Entry "9f86d081884c7d659a2feaa0c55ad015a3bf4f1b2b0b822cd15d6c15b0f00a08"

This example filters the results by blocked files.

Get-TenantAllowBlockListItems -ListType FileHash -Block

For detailed syntax and parameter information, see Get-TenantAllowBlockListItems.

Use the Microsoft 365 Defender portal to modify allow or block entries for files in the Tenant Allow/Block List

When you modify allow or block entries for files in the Tenant Allow/Block list, you can only modify the expiration date and notes.

  1. In the Microsoft 365 Defender portal at https://security.microsoft.com, go to Policies & rules > Threat Policies > Rules section > Tenant Allow/Block Lists. Or, to go directly to the Tenant Allow/Block List page, use https://security.microsoft.com/tenantAllowBlockList.

  2. Select the Files tab

  3. On the Files tab, select the check box of the entry that you want to modify, and then click the Edit icon. Edit button that appears.

  4. The following settings are available in the Edit file flyout that appears:

    • Remove allow entry after or Remove block entry after:

      • You can extend allow entries for a maximum of 30 days after the creation date.
      • You can extend block entries for a maximum of 90 days after the creation date or set them to Never expire.

    • Optional note

    When you're finished, click Save.

Note

For allow entries only, if you select the entry by clicking anywhere in the row other than the check box, you can select View submission icon. View submission in the details flyout that appears to go to the Submissions page at https://security.microsoft.com/reportsubmission.

Use PowerShell to modify allow or block entries for files in the Tenant Allow/Block List

In Exchange Online PowerShell, use the following syntax:

Set-TenantAllowBlockListItems -ListType <FileHash> <-Ids <Identity value> | -Entries <Value value>> [<-ExpirationDate Date | -NoExpiration>] [-Notes <String>]

This example changes the expiration date of the specified file block entry.

Set-TenantAllowBlockListItems -ListType FileHash -Entries "27c5973b2451db9deeb01114a0f39e2cbcd2f868d08cedb3e210ab3ece102214" -ExpirationDate "9/1/2022"

For detailed syntax and parameter information, see Set-TenantAllowBlockListItems.

Use the Microsoft 365 Defender portal to remove allow or block entries for files from the Tenant Allow/Block List

  1. In the Microsoft 365 Defender portal at https://security.microsoft.com, go to Policies & rules > Threat Policies > Rules section > Tenant Allow/Block Lists. Or, to go directly to the Tenant Allow/Block List page, use https://security.microsoft.com/tenantAllowBlockList.

  2. Select the Files tab.

  3. On the Files tab, do one of the following steps:

    • Select the check box of the entry that you want to remove, and then click the Delete icon. Delete icon that appears.
    • Select the entry that you want to remove by clicking anywhere in the row other than the check box. In the details flyout that appears, click Delete icon. Delete.

  4. In the warning dialog that appears, click Delete.

Note

You can select multiple entries by selecting each check box, or select all entries by selecting the check box next to the Value column header.

Use PowerShell to remove allow or block entries for files from the Tenant Allow/Block List

In Exchange Online PowerShell, use the following syntax:

Remove-TenantAllowBlockListItems -ListType FileHash <-Ids <Identity value> | -Entries <Value value>>

This example removes the specified file block from the Tenant Allow/Block List.

Remove-TenantAllowBlockListItems -ListType FileHash -Entries "27c5973b2451db9deeb01114a0f39e2cbcd2f868d08cedb3e210ab3ece102214"

For detailed syntax and parameter information, see Remove-TenantAllowBlockListItems.