Computer security is the process of preventing and detecting unauthorized use of your computer. Prevention measures help you to stop unauthorized users  from accessing any part of your computer system. Detection helps you to determine whether or not someone attempted to break into your system, if they were successful, and what they may have done.

Protect your hardware:
Safety and security start with protecting computers. Install a security suite (antivirus, antispyware, and firewall) that is set to update automatically. Keep your operating system, Web browser, and other software current as well and back up computer files on a regular basis.

Use strong passwords:
Make sure that your password is long, complex and combines, letters, numerals, and symbols. Ideally, you should use a different password for every online account you have. If you need to write down your password to remember it, store it somewhere away from your computer.

Email:
Before opening any email attachments, be sure you know the source of the attachment. It is not enough that the mail originated from an address you recognize. The Melissa virus spread precisely because it originated from a familiar address. Malicious code might be distributed in amusing or enticing programs.

Keep personal info personal:
Be cautious about how much personal information you provide on social networking sites. The more information you post, the easier it may be for a hacker or someone else to use that information to steal your identity, access your data, or commit other crimes such as stalking.