How to boost your malware defense and protect your PC

1. Install antivirus and antispyware programs from a trusted source
2. Never download anything in response to a warning from a program you didn't install or don't recognize that claims it will protect your PC or offers to remove viruses. It is highly likely to do the opposite.
3. Get reputable anti-malware programs from a vendor you trust.
4. Windows 8 includes antivirus protection called Windows Defender. It’s turned on by default.
5. If your computer is not running Windows 8, download Microsoft Security Essentials for free.
6. Choose security software that is compatible with Windows 7.

Update software regularly
Cybercriminals are endlessly inventive in their efforts to exploit vulnerabilities in software, and many software companies work tirelessly to combat these threats. That is why you should:

• Regularly install updates for all your software antivirus and antispyware programs, browsers (like Windows Internet Explorer), operating systems (like Windows), and word processing and other programs. 
• Subscribe to automatic software updates whenever they are offered for example, you can automatically update all Microsoft software. Windows 8 and Windows 7 turn on automatic updating during installation. 
• Uninstall software that you don't use. You can remove it using Windows Control Panel. 

Use strong passwords and keep them secret

• Strong passwords are at least 14 characters long and include a combination of letters, numbers, and symbols. 
• Don't share passwords with anyone. 
• Don’t use the same password on all sites. If it is stolen, all the information it protects is at risk. 
• Create different strong passwords for the router and the wireless key of your wireless connection at home. Find out how from the company that provides your router. 
• Use our password checker. 

Never turn off your firewall

• A firewall puts a protective barrier between your computer and the Internet. Turning it off for even a minute increases the risk that your PC will be infected with malware.
• Use flash drives cautiously
• Minimize the chance that you'll infect your computer with malware:
• Don't put an unknown flash (or thumb) drive into your PC. 
• Hold down the SHIFT key when you insert the drive into your computer. If you forget to do this, click in the upper-right corner to close any flash drive-related pop-up windows. 
• Don't open any files on your drive that you have not expected to see. 
• Don't be tricked into downloading malware 

Instead, follow this advice:

• Be very cautious about opening an attachment or clicking a link in an email, instant message, or post on social networks (like Facebook) even if you know the sender. Call to ask if a friend sent it; if not, delete it or close the IM window. 
• Avoid clicking Agree, OK, or I accept in banner ads, in unexpected pop-up windows with warnings or offers to remove spyware or viruses, or on websites that may not seem legitimate. 
• Instead, press CTRL + F4 on your keyboard to close the window. 
• If the window doesn't close, press ALT + F4 on your keyboard to close the browser. If asked, close all tabs and don’t save any tabs for the next time you start the browser. 
• Only download software from websites you trust. Be cautious of "free" offers of music, games, videos, and the like. They are notorious for including malware in the download. 
• Take advantage of technology such as Windows SmartScreen in Windows 8 designed to help protect you from phishing scams and new malware that your anti-malware software hasn't detected yet. 

Malicious Code

Malicious code, or malware, is a common name applied to all forms of unwanted and destructive software, such as viruses, worms, and Trojans. The best way to protect from malicious code is to install virus scanners and keep virus definition (signature) files current.

Virus: A virus is malicious code that infects or attaches itself to other objects or programs. All viruses have some form of replication mechanism, which is how they propagate.

Worm: A worm is malicious code that replicates by making copies of itself on the same computer or by sending copies of itself to another computer. Worms, unlike viruses, do not infect other program files on a computer. All worms have some form of replication mechanism, which is how they propagate. A worm does not require any host program unlike virus to execute, they can run independently.

Trojan: A Trojan horse is seemingly useful (or harmless) programs that perform malicious or illicit action then activated, such as destroying files. For example, user downloads what appears to be a movie or music file but he unleash a dangerous program which can erase in disk or can send his credit card numbers or password files to intruders. These backdoor programs may also open certain ports on user computer allowing unauthorized access to user computer.

The malicious code usually propagates through email attachments.