Mark is the Administrator of a Linux computer. He wants to check the status of failed Telnet-based login attempts on the Linux computer. Which of the following shell commands will he use to…

GREP searches through Linux log files such as /var/log/auth.log or /var/log/secure for text patterns like 'Failed' or 'telnet', allowing an administrator to isolate and review failed authentication events. It is the standard Unix utility for pattern-based log filtering and is widely used in security auditing and incident investigation workflows.

CP is the file copy command used to duplicate files or directories and has no capability to search or filter log file content.

FSCK (File System Consistency Check) is a utility for checking and repairing Linux file system integrity and does not read or parse log files for authentication events.

CAT outputs the entire contents of a file to the terminal sequentially but cannot filter or search for specific patterns such as failed login entries.