Computer data often travels from one computer to another, leaving the safety of its protected physical surroundings. Once the data is out of hand, people with bad intention could modify or forge your data, either for amusement or for their own benefit.
Cryptography can reformat and transform our data, making it safer on its trip between computers. The technology is based on the essentials of secret codes, augmented by modern mathematics that protects our data in powerful ways.
Computer Security - generic name for the collection of tools designed to protect data and to thwart hackers
Network Security - measures to protect data during their transmission
Internet Security - measures to protect data during their transmission over a collection of interconnected networks