Brute force attacks involve identifying a valid user account and then bombarding the server with an extensive:

List of possible passwords in search of the one password that will gain access to a system.

Explanation:

A brute force attack is a way of trying to gain illegal access into a password-protected website by using various combinations of passwords repetitively until you get the right one.

Programs and bots such as Crack, Hashcat, Rainbowcrack etc are used by hackers to perform brute force attack with the motive of stealing valuable data or taking over a website shutting it down.

Tools used in securing websites against such attacks work by denying a user or an IP address, after a limited number of wrong attempts. Such softwares include Deny and Fail2ban.