(a) (i) Define computer virus. (i) List three types of computer network security breach. (b) State five sources of computer network security breach.

(a)(i) Definition of computer virus

A computer virus is a malicious program written to attach itself to other programs or files and to replicate itself, so that it can spread from one computer to another and damage, corrupt or interfere with the normal working of the system.

(a)(ii) Three types of computer network security breach

1. Hacking / unauthorised access to the network.
2. Virus, worm or malware infection.
3. Denial of Service (DoS) attack that floods the network so genuine users are shut out. (Other acceptable answers: phishing, eavesdropping/interception, spoofing.)

(b) Five sources of computer network security breach

1. Infected external storage media such as flash drives and memory cards.
2. Downloads and e-mail attachments from untrusted Internet sites.
3. Hackers and intruders attacking the network from outside.
4. Dishonest or careless insiders (staff or users who misuse access rights or leak passwords).
5. Weak or missing security measures such as poor passwords, unpatched software and lack of a firewall or anti-virus.