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FTP Request Filtering

Published: February 29, 2012

Updated: February 29, 2012

Applies To: Windows Server 2012, Windows Server 2012 R2



Use the FTP Request Filtering feature page to define the request filtering settings for your FTP site. FTP request filtering is a security feature that allows internet service providers (ISPs) and application service providers to restrict protocol and content behavior. For example, using the File Name Extensions tab you can specify a list of file name extensions that are allowed or denied.

Related scenarios

In this document

The following tables describe the UI elements that are available on the feature page and in the Actions pane.

 

Element Name Description

File Name Extensions

Specifies a list of file name extensions for which the FTP service allows or denies access.

Hidden Segments

Specifies a list of hidden segments for which the FTP service denies access and does not display in directory listings.

Denied URL Sequences

Specifies a list of URL sequences for which the FTP service denies access.

Commands

Specifies a list of FTP commands for which the FTP service allows or denies access.

 

Element Name Description

Edit Feature Settings

Opens the Edit FTP Request Filtering Settings dialog box for you to configure general properties and FTP request limits.

Allow File Name Extension

Opens the Allow File Name Extension dialog box for you to add a file name extension to the list of allowed file name extensions.

Deny File Name Extension

Opens the Deny File Name Extension dialog box for you to add a file name extension to the list of denied file name extensions.

Add Hidden Segment

Opens the Add Hidden Segment dialog box for you to add a hidden segment to the list of hidden segments.

Add URL Sequence

Opens the Add Deny URL Sequence dialog box for you to add a URL sequence to the list of denied URL sequences.

Allow Command

Opens the Allow Command dialog box for you to add an FTP command to the list of allowed FTP commands.

Deny Command

Opens the Deny Command dialog box for you to add an FTP command to the list of denied FTP commands.

WarningWarning
Using this feature incorrectly can prevent access to your server. For example, if you deny access to the USER and PASS commands, users are not able to log in to your FTP server.

Remove

Removes a file name extension, hidden segment, URL sequence, or command from the list.

Use FTP File Name Extensions to define the list of file name extensions for which the FTP service will either allow or deny access. Configuring specific file name extensions allows web server administrators to customize which file name extensions that the FTP service allows or denies, which you can use to tighten security on your server. For example, if you deny access to *.exe and *.com files, you can prevent internet clients from uploading executable files to your web server.

noteNote
The Edit FTP Request Filtering Settings dialog box allows you to specify whether unlisted file name extensions are allowed. You can fine-tune the file access restrictions for your server by specifying that unlisted file name extensions are not allowed, and using the FTP File Name Extensions feature to manually specify the list of file name extensions that are allowed on your server.

 

Element Name Description

File Name Extension

Displays the file name extension for which the FTP service either allows or denies access.

Allowed

Displays the status of the file name extension, which will be either True if the file name extension is allowed, or False if the file name extension is denied.

 

Element Name Description

Allow File Name Extension

Opens the Allow File Name Extension dialog box for you to add a file name extension to the list of allowed file name extensions.

Deny File Name Extension

Opens the Deny File Name Extension dialog box for you to add a file name extension to the list of denied file name extensions.

Remove

Removes a file name extension, hidden segment, URL sequence, or command from the list.

Edit Feature Settings

Opens the Edit FTP Request Filtering Settings dialog box for you to configure general properties and FTP request limits.

Use the Allow File Name Extension or Deny File Name Extension dialog box to add a file name extension to the list of file name extensions for which the FTP service will either allow or deny access.

 

Element Name Description

File name extension

Specifies the file name extension for which the FTP service either allows or denies access.

Use FTP Hidden Segments to define the list of URL segments for which the FTP service will deny access and will not display in directory listings. For example, to prevent access to the Bin directory of your web application, you could add the Bin directory as a hidden segment for your FTP site. When an FTP client logs in to your FTP site, the Bin folder is not displayed in directory listings. If the FTP client attempts to change to the Bin folder, the FTP service returns an access denied error message to the FTP client.

 

Element Name Description

Segment

Displays the URL segment for which the FTP service denies access and does not display in directory listings.

 

Element Name Description

Add Hidden Segment

Opens the Add Hidden Segment dialog box for you to add a hidden segment to the list of hidden segments.

Remove

Removes a hidden segment from the list.

Edit Feature Settings

Opens the Edit FTP Request Filtering Settings dialog box for you to configure general properties and FTP request limits.

Use the Add Hidden Segment dialog box to add a URL segment to the list of URL segments for which the FTP service will deny access.

 

Element Name Description

Hidden segment

Specifies the URL segment for which the FTP service denies access.

noteNote
The FTP service does not show hidden segments in directory listings.

Use FTP Denied URL Sequences to define the list of URL sequences for which the FTP service will deny access. For example, to prevent access to the Bin directory of your web application, you could add the Bin directory as a denied URL sequences for your FTP site. When an FTP client logs in to your FTP site, the Bin folder is displayed in directory listings; however, if the FTP client attempts to change to the Bin folder, the FTP service returns an access denied error message to the FTP client.

 

Element Name Description

URL Sequence

Displays the FTP URL sequence for which the FTP service denies access.

 

Element Name Description

Add URL Sequence

Opens the Add Deny Sequence dialog box for you to add a URL sequence to the list of denied URL sequences.

Remove

Removes a file name extension, hidden segment, URL sequence, or command from the list.

Edit Feature Settings

Opens the Edit FTP Request Filtering Settings dialog box for you to configure general properties and FTP request limits.

Use the FTP Add Deny Sequence dialog box to add a URL sequence to the list of URL sequences for which the FTP service will deny access.

 

Element Name Description

URL sequence

Specifies the URL sequence for which the FTP service denies access.

Use the Edit FTP Request Filtering Settings dialog box to specify general FTP request filtering settings, request limits, and command filtering options.

 

Element Name Description

Allow unlisted file name extensions

Select this option to allow unlisted file name extensions.

Allow high-bit characters

Select this option to allow high-bit characters in FTP operations.

Maximum content length (Bytes)

Specifies the maximum length, in bytes, for FTP content.

noteNote
Specifying zero (0) means unlimited.

Maximum URL length (Bytes)

Specifies the maximum length, in bytes, for an FTP URL.

Maximum command length (Bytes)

Specifies the maximum length, in bytes, for an FTP command.

Allow unlisted commands

Select this option to allow FTP commands that are not in the FTP Commands list.

Use FTP Commands to define the list of commands for which the FTP service will either allow or deny access. Configuring specific commands allows Web server administrators to customize the list of FTP commands that the FTP service allows, which you can use to tighten security on your server. For example, if you deny access to the FTP SYST command, you can prevent internet clients from determining your server's operating system.

noteNote
The Edit FTP Request Filtering Settings dialog box allows you to specify whether unlisted commands are allowed, which you can use to manually specify which commands are allowed.

WarningWarning
Using the FTP Commands feature incorrectly can prevent access to your FTP server. For example, if you deny access to the USER or PASS commands, users are not able to log in to your FTP server. In addition, even though you could specify that unlisted commands are not allowed in the Edit FTP Request Filtering Settings dialog box and use the Commands list to specify only the FTP commands that are allowed, this configuration is not recommended due to the complexity involved in specifying the correct list of FTP commands that are required for normal FTP operation.

 

Element Name Description

Command

Displays the FTP command for which the FTP service either allows or denies access.

Allowed

Displays the status of the FTP command, which will be either True if the FTP command is allowed, or False if the FTP command is denied.

 

Element Name Description

Allow Command

Opens the Allow Command dialog box for you to add an FTP command to the list of allowed FTP commands.

Deny Command

Opens the Deny Command dialog box for you to add an FTP command to the list of denied FTP commands.

WarningWarning
Using this feature incorrectly can prevent access to your server. For example, if you deny access to the USER and PASS commands, users are not able to log in to your FTP server.

Remove

Removes an FTP command from the list.

Edit Feature Settings

Opens the Edit FTP Request Filtering Settings dialog box for you to configure general properties and FTP request limits.

Use the Allow Command or Deny Command dialog box to add an FTP command to the list of commands for which the FTP service will either allow or deny access.

WarningWarning
Using this feature incorrectly can prevent access to your server. For example, if you deny access to the USER and PASS commands, users are not able to log in to your FTP server.

 

Element Name Description

Command

Specifies the FTP command for which the FTP service either allows or denies access.

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