cyberstrikeus CIS Ubuntu Linux 16.04 LTS Benchmark v2.0.0 - Control 5.3.23
Description
The MaxSessions parameter Specifies the maximum number of open sessions permitted per network connection.
Rationale
To protect a system from denial of service due to a large number of concurrent sessions, use the rate limiting function of MaxSessions to protect availability of sshd logins and prevent overwhelming the daemon.
Audit Procedure
Command Line
Run the following command and verify that output MaxSessions is 10 or less:
sshd -T -C user=root -C host="$(hostname)" -C addr="$(grep $(hostname) /etc/hosts | awk '{print $1}')" | grep -i maxsessions
Expected Result
maxsessions 10
Run the following command and verify the output:
grep -Ei '^\s*MaxSessions\s+(1[1-9]|[2-9][0-9]|[1-9][0-9][0-9]+)' /etc/ssh/sshd_config
Nothing should be returned.
Remediation
Command Line
Edit the /etc/ssh/sshd_config file to set the parameter as follows:
MaxSessions 10
Default Value
MaxSessions 10
References
- SSHD_CONFIG(5)
CIS Controls
Version 7
5.1 Establish Secure Configurations - Maintain documented, standard security configuration standards for all authorized operating systems and software.
Profile Applicability
- Level 1 - Server
- Level 1 - Workstation
Assessment Status
Automated