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).
Some of the common ethical issues are listed below:
1. Cyber crime
2. Software Piracy
3. Hacking
4. Use of computers to commit fraud
5. Sabotage in the form of viruses
6. Making false claims using computers.

Generally, the following guidelines should be observed by computer users.
1. Honesty: Users should be truthful while using the internet.
2. Confidentiality: Users should not share any important information with unauthorized people.
3. Respect: Each user should respect the privacy of other users.
4. Responsibility: Each user should take ownership and responsibility for their actions.

1. Symmetric encryption is a technique to use the same key for both encryption and decryption. The main disadvantage of the symmetric key encryption is that all authorized persons involved, have to exchange the key used to encrypt the data before they can decrypt it. If anybody intercepts the key information, they may read all message.
2. The following Figure depicts the working of symmetric key encryption.

(i) Encryption: Encryption is the process of translating the plain text data(plaintext) into random and mangled data (called cipher-text).
(ii) Decryption: Decryption is the reverse process of converting the cipher-text back to plaintext Encryption and decryption are done by cryptography: In cryptography a key is a piece of information (parameter) that determines the functional output of a cryptographic algorithm.

1. A fire wall is a computer network security based system that monitors and controls incoming and outgoing network traffic based on predefined security rules.
2. A firewall commonly establishes a block between a trusted internal computer network and entrusted computer outside the network.