2. Hackers They can u Read the data files u Run the application programs u Modify some files which may cause damages Individuals who gain unauthorized access to computer systems.

3. Ways hackers use to invade the computer system n 1. Tapping Information theft can tap into communication line and steal the data without interrupting the sending and receiving of data. SENDER RECEIVER Communication media (e.g. network/ telephone line) HACKER ADD The message “ADD” is duplicated by the hacker.

4. To overcome this problem, we can use data encryption method to help us because it is hard or even impossible to impose a physical protection or password during this process. Data Encryption n Data are usually encrypted before sending and decrypted upon receiving. A method of converting a meaningful message into an encrypted form which does not carry any meaning.

5. Example: Given the encrypted form is HKK. Knowing this key. Change every letter in the message to another one. SENDER RECEIVER Communication media (e.g. network/ telephone line) HKK ADD HKK

6. 2. Denial of Service Definition: A prevention of the use of information resources either intentionally or unintentionally, which affects the availability of the information resources. n Hackers send large amount of meaningless messages or e-mail to target. n Make the server not able to react with large amount of information at the same time. n Computer may react very slowly and cause the service to stop.

7. 3. Change/ Delete information in a web site. 4. Transmit computer virus or infected programs through e-mail. (e.g. I Love You) 5. Unauthorized use of others password and access user’s information without permission.

8. Data Protection Methods n 1. Use password that is hard to guess. n 2. Install anti-virus software. n 3. Install firewall software. n 4. Use encryption whenever possible