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CIS Ubuntu 14.04 LTS - 5.2.5 Ensure SSH MaxAuthTries is set to 4 or less

DevOps & Security
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Verify SSH MaxAuthTries is set to 4 or less to limit brute force attack risk

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Source SKILL.md: https://github.com/CyberStrikeus/CyberStrike/blob/HEAD/.cyberstrike/skill/CIS_benchmarks/Operating_Systems/Ubuntu/CIS_Ubuntu_Linux_14.04_LTS_Benchmark_v2.1.0/cis-ubuntu1404-v210-5-2-5/SKILL.md

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5.2.5 Ensure SSH MaxAuthTries is set to 4 or less (Scored)

Profile Applicability

  • Level 1 - Server
  • Level 1 - Workstation

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

Run the following command and verify that output MaxAuthTries is 4 or less:

grep "^MaxAuthTries" /etc/ssh/sshd_config

Expected Result

MaxAuthTries 4

Remediation

Edit the /etc/ssh/sshd_config file to set the parameter as follows:

MaxAuthTries 4

Default Value

MaxAuthTries 6

References

  • CIS Controls: 16 - Account Monitoring and Control

Profile

  • Level 1 - Server
  • Level 1 - Workstation