A typical attacker follows some steps:

* Identify the target system

* Gathering information about the targeted system

* Finding the possible loopholes

* Exploiting those loopholes

* Escaping without a trace

Types of attacks the system might face:

It is the responsibility of the administrator to protect the system from various attacks. Some types of attacks:

* DOS attacks

          Flooding a host with sufficient network traffic.

* Theft from key logging

          Logging the key strokes that the user presses.

* Trojan attacks

* Brute force attack

          Trial and error used to guess a user’s username, password, credit card number.

* IP Spoofing

          Faking the original IP address.

* Phreaking

          Form of cracking the telecom networks.

* Cross Site Scripting (XSS)

          Inserting the scripted code into another site’s web page.

* Phishing

          Getting someone’s personal information through emails.

How to prevent your system from hackers:
*  Keep your antivirus up-to date

* Patch the security holes frequently if you have knowledge about system.

* Turn on firewall.

* Try to maintain backup of your system.

* Setup intrusion detection systems.

* Encrypt your important data.

* Avoid entertaining untrusted pop-ups.

*  Use anti-key loggers.

* If you are accessing your accounts on some other systems make sure that there are no key loggers installed on that otherwise use virtual keyboard.

Because hackers can affect your system adversely there are people who help you from hackers. These are ethical hackers.