Worms are self- repeating and do not require a computer program to attach themselves. Worms continually look for vulnerabilities and report back to the author of the worm when weaknesses are discovered.

A virus is a small piece of computer code that can repeat itself and spreads from one computer to another by attaching itself to another computer file.

It is a malicious practice in which communication is send from unknown source disguised as a source known to the receiver

Cybercrime is an intellectual, white-collar crime. Those who commit such crimes generally manipulate the computer system in an intelligent manner.

A cookie (also called HTTP cookie, web cookie, Internet cookie, browser cookie, or simply cookie) is a small piece of data sent from a website and stored on the user's computer memory (Hard drive) by the user's web browser while the user is browsing internet.

Cracking is where someone edits a program source so that the code can be exploited or modified. "Cracking" means trying to get into computer systems in order to steal, corrupt, or illegitimately view data.

A person or program collects login and password information from a legitimate user to illegally gain access to others, account(s).

There are two types of encryption schemes as listed below:
Symmetric Key encryption:
Symmetric encryption is a technique to use the same key for both encryption and decryption.

Public Key encryption:
Public key encryption is also called Asymmetric encryption. It uses the concept of a key value pair, a different key is used for the encryption and decryption process.

Ethics means "What is wrong and What is Right". It is a set of moral principles that rule the behavior of individuals who use computers. An individual gains knowledge to follow the right behavior, using morals that are also known as ethics. Morals refer to the generally accepted standards of right and wrong in the society. Similarly, in cyber-world, there 'are certain standards such as
1. Do not use pirated software
2. Do not use unauthorized user accounts
3. Do not steal others' passwords
4. Do not hack

An Ethical issue is a problem or issue that requires a person or organization to choose between alternatives that must be evaluated as right (ethical) or wrong (unethical). These issues must be addressed and resolved to have a positive influence in society.
Some of the common ethical issues are listed below:
(i) Cyber crime
(ii) Software Piracy
(iii) Unauthorized Access
(iv) Hacking
(v) Use of computers to commit fraud
(vi) Sabotage in the form of viruses.

A proxy server provides a gateway between users and the internet. It is a server, referred to as an “intermediary” because it goes between end-users and the web pages they visit online. A proxy server is essentially a computer on the internet that has an IP address of its own.

A firewall is a computer network security based system that monitors and controls incoming and outgoing network traffic based on predefined security rules. A firewall commonly establishes a block between a trusted internal computer network and entrusted computer outside the network. They are generally categorized as network-based or host-based. Network based firewalls are positioned on the gateway computers of LANs [local area Network], WANS [Wide Area Network] and intranets.