Explanation
chmod is a Linux command that can be used to change or modify the permissions of files and directories. The
/etc/shadow file is a system file that stores the encrypted passwords of user accounts in Linux. The
/etc/shadow file should have restricted permissions to prevent unauthorized access or modification of the passwords. The recommended permissions for the /etc/shadow file are read/write for root user only (600). If the systems administrator observes that the /etc/shadow file has permissions beyond the baseline recommendation, they can use the chmod command to resolve this issue by setting the appropriate permissions for the file. For example, chmod 600 /etc/shadow would set the permissions of the /etc/shadow file to read/write for root user only. 181920 References: CompTIA Security+ SY0-601 Certification Study Guide, Chapter 9: Implementing Identity and Access Management Controls, page 404; chmod - Wikipedia; Linux
/etc/shadow file - nixCraft; How to Change File Permissions in Linux - Linuxize