Optional Subsystems are permitted to operate on the system.

From Windows 2008 Domain Controller Security Technical Implementation Guide

Associated with IA controls: ECSC-1

SV-29734r1_rule Optional Subsystems are permitted to operate on the system.

Vulnerability discussion

The POSIX subsystem is an Institute of Electrical and Electronic Engineers (IEEE) standard that defines a set of operating system services. The POSIX Subsystem is required if the server supports applications that use that subsystem. The subsystem introduces a security risk relating to processes that can potentially persist across logins. That is, if a user starts a process and then logs out, there is a potential that the next user who logs in to the system could access the previous users process. This is dangerous because the process started by the first user may retain that users system privileges; anything the second user does with that process will be performed with the privileges of the first user.

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Fix text

Configure the policy value for Computer Configuration -> Windows Settings -> Security Settings -> Local Policies -> Security Options -> “System Settings: Optional Subsystems” to “Blank” (Configured with no entries).

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