The IIS 10.0 website must have resource mappings set to disable the serving of certain file types.

Overview

Finding ID	Version	Rule ID	IA Controls	Severity
V-218745	IIST-SI-000216	SV-218745r558649_rule		Medium

Description
IIS 10.0 will either allow or deny script execution based on file extension. The ability to control script execution is controlled through two features with IIS 10.0, Request Filtering and Handler Mappings. For Request Filtering, the ISSO must document and approve all allowable file extensions the website allows (white list) and denies (black list) by the website. The white list and black list will be compared to the Request Filtering in IIS 10.0. Request Filtering at the site level take precedence over Request Filtering at the server level.

Description

IIS 10.0 will either allow or deny script execution based on file extension. The ability to control script execution is controlled through two features with IIS 10.0, Request Filtering and Handler Mappings. For Request Filtering, the ISSO must document and approve all allowable file extensions the website allows (white list) and denies (black list) by the website. The white list and black list will be compared to the Request Filtering in IIS 10.0. Request Filtering at the site level take precedence over Request Filtering at the server level.

STIG	Date
Microsoft IIS 10.0 Site Security Technical Implementation Guide	2021-12-28

Details

Check Text ( C-20218r311133_chk )
For Request Filtering, the ISSO must document and approve all allowable scripts the website allows (white list) and denies (black list). The white list and black list will be compared to the Request Filtering in IIS 10.0. Request Filtering at the site level take precedence over Request Filtering at the server level. Follow the procedures below for each site hosted on the IIS 10.0 web server: Open the IIS 10.0 Manager. Click the site name to review. Double-click Request Filtering->File Name Extensions Tab. If any script file extensions from the black list are not denied, this is a finding.

Check Text ( C-20218r311133_chk )

For Request Filtering, the ISSO must document and approve all allowable scripts the website allows (white list) and denies (black list). The white list and black list will be compared to the Request Filtering in IIS 10.0. Request Filtering at the site level take precedence over Request Filtering at the server level.

Follow the procedures below for each site hosted on the IIS 10.0 web server:

Open the IIS 10.0 Manager.

Click the site name to review.

Double-click Request Filtering->File Name Extensions Tab.

If any script file extensions from the black list are not denied, this is a finding.

Fix Text (F-20216r311134_fix)
Follow the procedures below for each site hosted on the IIS 10.0 web server: Open the IIS 10.0 Manager. Click the site name to review. Double-click Request Filtering->File Name Extensions Tab->Deny File Name Extension. Add any script file extensions listed on the black list that are not listed. Select "Apply" from the "Actions" pane.