Many malware closely associate with certain file type extensions (examples: .doc, .exe, .dll). The file's extension identifies the file type. Similarly, specific attacks often associate with a specific file name. Cloud App Security can block files according to the file type, file name, file extension, or file contents that contain suspicious URLs.
For email services, file blocking prevents email messages containing suspicious attachments from delivering to recipients. Policy actions include replacing the file with a benign text file, quarantining or deleting all email messages with attachments that violate specified policies, or labeling the violating email messages as risky in recipient's mailbox (Gmail only).
For the other cloud applications, file blocking prevents suspicious files from entering these applications. Policy actions include quarantining or deleting files that violate specified policies.
Trend Micro recommends temporarily quarantining all high-risk file types and known malware file names. This way, you can examine the quarantine folder and take action on detected files when you have more time.
Option | Description |
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Apply to |
(Exchange Online and Gmail only) Select the scope of email messages that File Blocking applies to.
Note:
For details about internal domains, see Configuring Internal Domains For Exchange Online (Inline Mode), the scope is fixed to Inbound messages for inbound protection and Outbound messages for outbound protection. Inbound messages are sent from outside your organization to an address inside the organization, while outbound messages are sent from your organization to external addresses. |
Type of File Blocking |
Select whether to block all files or specific files. |
Blocking list |
If Type of File Blocking is set to "Block All Files":
If Type of File Blocking is set to "Block Specific Files":
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Compressed Files |
Select the check box to scan for excluded file extensions and file names inside compressed files. |
This feature is available to Gmail, Exchange Online, and Exchange Online (Inline Mode).
Be aware that for individual email addresses, wildcard characters and regular expressions are not supported. To approve all senders from a domain, type *@domain, for example, *@example.com.
A maximum of 1,024 email addresses or domains can be added to the Approved Sender list.
Make sure that each email address occupies a separate line in the .txt file.
Cloud App Security protects cloud applications and services by executing specified actions after detecting a file that matches scanning conditions. The action depends on the performed scan, the affected application or service, and the configured actions for that scan.
For details about the actions, see Actions Available for Different Services.
Option | Description |
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Notify administrator |
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Notify User |
Exchange Online and Gmail: Specify message details that notify recipients that Cloud App Security detected a security risk and took action on their email message or attachment. SharePoint Online, OneDrive, Microsoft Teams (Teams), Box, Dropbox, and Google Drive: Specify message details that notify the user who updated a file that Cloud App Security detected a security risk and took action on their file. Teams Chat: Cloud App Security does not provide this option. When a chat message was blocked, a notification "This message was blocked." provided by Microsoft appears in the sender's private chat window. Message senders can click What can I do? to view more information about the blocked messages. Salesforce: Specify message details that notify the user who updated a Salesforce object record that Cloud App Security detected a security risk and took action on the update. |
When specifying a notification message, include relevant tokens and edit the message content as desired. For details about tokens, see Token List.