5.2.12 Ensure only approved MAC algorithms are used

Information

MD5 and 96-bit MAC algorithms are considered weak and have been shown to increase exploitability in SSH downgrade attacks. Weak algorithms continue to have a great deal of attention as a weak spot that can be exploited with expanded computing power. An attacker that breaks the algorithm could take advantage of a MiTM position to decrypt the SSH tunnel and capture credentials and information

NOTE - Nessus has not performed this scan. Please ensure the configuration complies with site policy.

Solution

Edit the /etc/ssh/sshd_config file to set the parameter in accordance with site policy. The following includes all supported and accepted MACs: MACs hmac-sha2-512,hmac-sha2-256

See Also

https://benchmarks.cisecurity.org/tools2/linux/CIS_Amazon_Linux_Benchmark_v2.0.0.pdf

Item Details

Category: SYSTEM AND COMMUNICATIONS PROTECTION

References: 800-53|SC-13

Plugin: Unix

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