In this, we used the cat and grep commands. The most common use of the cat command is to display the contents of a file, and grep is a Linux utility used for searching a file for a particular pattern; then, it will display the lines that will have the particular pattern.
In the previous examples, we were searching for a failed login attempt. We are matching such key words using the grep command and then we are displaying it using the cat command.
To block an IP address, we just added a single line into the hosts.deny file, which will block that particular IP address.
