cyberstrikeus CIS Ubuntu Linux 16.04 LTS Benchmark v2.0.0 - Control 5.3.8
Description
The MaxAuthTries parameter specifies the maximum number of authentication attempts permitted per connection. When the login failure count reaches half the number, error messages will be written to the syslog file detailing the login failure.
Rationale
Setting the MaxAuthTries parameter to a low number will minimize the risk of successful brute force attacks to the SSH server. While the recommended setting is 4, set the number based on site policy.
Audit Procedure
Command Line
Run the following command and verify that output MaxAuthTries is 4 or less:
sshd -T -C user=root -C host="$(hostname)" -C addr="$(grep $(hostname) /etc/hosts | awk '{print $1}')" | grep maxauthtries
Expected Result
maxauthtries 4
Run the following command and verify that the output:
grep -Ei '^\s*maxauthtries\s+([5-9]|[1-9][0-9]+)' /etc/ssh/sshd_config
Nothing is returned.
Remediation
Command Line
Edit the /etc/ssh/sshd_config file to set the parameter as follows:
MaxAuthTries 4
Default Value
MaxAuthTries 6
References
- SSHD_CONFIG(5)
CIS Controls
Version 7
16.13 Alert on Account Login Behavior Deviation - Alert when users deviate from normal login behavior, such as time-of-day, workstation location and duration.
Profile Applicability
- Level 1 - Server
- Level 1 - Workstation
Assessment Status
Automated