The macOS system must limit the number of concurrent SSH sessions to 10 for all accounts and/or account types.

Overview

Finding ID	Version	Rule ID	IA Controls	Severity
V-209545	AOSX-14-000050	SV-209545r507076_rule		Medium

Description
Operating system management includes the ability to control the number of users and user sessions that utilize an operating system. Limiting the number of allowed users and sessions per user is helpful in reducing the risks related to DoS attacks. This requirement addresses concurrent sessions for information system accounts and does not address concurrent sessions by single users via multiple system accounts. The maximum number of concurrent sessions should be defined based upon mission needs and the operational environment for each system.

Description

Operating system management includes the ability to control the number of users and user sessions that utilize an operating system. Limiting the number of allowed users and sessions per user is helpful in reducing the risks related to DoS attacks. This requirement addresses concurrent sessions for information system accounts and does not address concurrent sessions by single users via multiple system accounts. The maximum number of concurrent sessions should be defined based upon mission needs and the operational environment for each system.

STIG	Date
Apple OS X 10.14 (Mojave) Security Technical Implementation Guide	2020-09-11

Details

Check Text ( C-9796r282117_chk )
To verify that SSHD is limited to 10 sessions, use the following command: /bin/cat /etc/ssh/sshd_config \| grep MaxSessions The command must return "MaxSessions 10". If it returns null, or a commented value, or the value is greater than "10", this is a finding.

Fix Text (F-9796r282118_fix)
To configure SSHD to limit the number of sessions, use the following command: /usr/bin/sudo /usr/bin/sed -i.bak 's/^[\#]MaxSessions./MaxSessions 10/' /etc/ssh/sshd_config