Internet plays vital role in today’s world. It's utilized in education, business, shopping, social networking and other critical
infrastructures are dependent upon it for their day-to-day operation. This has increased risk of computer systems connected to the
web becoming targets of intrusions by cyber criminals. Cyber criminals attack systems to realize unauthorized access to
information, misuse information or to scale back the supply of data to authorized users. This leads to huge financial losses to
companies besides losing their goodwill to customers. Intrusion prevention techniques like user authentication (e.g. using password
or biometrics), information protection (e.g. encryption), avoiding programming errors and firewalls have been adopted to protect the
computer systems. But, unfortunately these intrusion prevention techniques alone aren't adequate
