Describe the dictionary attack and how it can be avoided.

What will be an ideal response?

A common attack frequently used against Linux systems is called a dictionary attack. This type of attack uses a password-cracking program that identifies passwords by simply trying one word after another from a dictionary file, including some common variations of these words. With today's computing power, a simple password can be cracked within minutes.
Therefore, a password should never be a word which could be found in a dictionary. A good, secure password should always be at least eight characters long and contain numbers along with uppercase characters.