network security:

1. Bob changes the amount on Alices cheque from $1000 to $10000. What types of intrusion does this represent? What are the security goals violated?

2.Alice gains access to a mail server of a company and broadcasts a fictitious email to all the employees. What type of intrusion does this represent? What are the security goals violated?

3.Name any two techniques for the prevention of DoS attacks.

4.Why does a virus-typically contain code to compress the file that it infects?

5.What is the difference between a virus and a worm?