The IIS 8.5 websites connectionTimeout setting must be explicitly configured to disconnect an idle session.

Overview

Finding ID	Version	Rule ID	IA Controls	Severity
V-76841	IISW-SI-000236	SV-91537r2_rule		Medium

Description
Leaving sessions open indefinitely is a major security risk. An attacker can easily use an already authenticated session to access the hosted application as the previously authenticated user. By closing sessions after a set period of inactivity, the web server can make certain that those sessions that are not closed through the user logging out of an application are eventually closed. Acceptable values are 5 minutes for high-value applications, 10 minutes for medium-value applications, and 20 minutes for low-value applications.

Description

Leaving sessions open indefinitely is a major security risk. An attacker can easily use an already authenticated session to access the hosted application as the previously authenticated user. By closing sessions after a set period of inactivity, the web server can make certain that those sessions that are not closed through the user logging out of an application are eventually closed. Acceptable values are 5 minutes for high-value applications, 10 minutes for medium-value applications, and 20 minutes for low-value applications.

STIG	Date
IIS 8.5 Site Security Technical Implementation Guide	2018-04-06

Details

Check Text ( C-76497r2_chk )
Follow the procedures below for each site hosted on the IIS 8.5 web server: Open the IIS 8.5 Manager. Click the site name. Select "Configuration Editor" under the "Management" section. From the "Section:" drop-down list at the top of the configuration editor, locate "system.web/sessionState". Verify the "timeout" is set to "00:20:00 or less”, using the lowest value possible depending upon the application. Acceptable values are 5 minutes for high-value applications, 10 minutes for medium-value applications, and 20 minutes for low-value applications. If "timeout" is not set to "00:20:00 or less”, this is a finding.

Check Text ( C-76497r2_chk )

Follow the procedures below for each site hosted on the IIS 8.5 web server:

Open the IIS 8.5 Manager.

Click the site name.

Select "Configuration Editor" under the "Management" section.

From the "Section:" drop-down list at the top of the configuration editor, locate "system.web/sessionState".

Verify the "timeout" is set to "00:20:00 or less”, using the lowest value possible depending upon the application.
Acceptable values are 5 minutes for high-value applications, 10 minutes for medium-value applications, and 20 minutes for low-value applications.

If "timeout" is not set to "00:20:00 or less”, this is a finding.

Fix Text (F-83537r2_fix)
Follow the procedures below for each site hosted on the IIS 8.5 web server: Open the IIS 8.5 Manager. Click the site name. Select "Configuration Editor" under the "Management" section. From the "Section:" drop-down list at the top of the configuration editor, locate "system.web/sessionState". Set the "timeout" to "00:20:00 or less”, using the lowest value possible depending upon the application. Acceptable values are 5 minutes for high-value applications, 10 minutes for medium-value applications, and 20 minutes for low-value applications. In the "Actions" pane, click "Apply".

Fix Text (F-83537r2_fix)

Follow the procedures below for each site hosted on the IIS 8.5 web server:

Open the IIS 8.5 Manager.

Click the site name.

Select "Configuration Editor" under the "Management" section.

From the "Section:" drop-down list at the top of the configuration editor, locate "system.web/sessionState".

Set the "timeout" to "00:20:00 or less”, using the lowest value possible depending upon the application.
Acceptable values are 5 minutes for high-value applications, 10 minutes for medium-value applications, and 20 minutes for low-value applications.

In the "Actions" pane, click "Apply".