Adware

• Adware is any application that displays user-targeted advertising by collecting personal information about your system, Internet browsing habits and program use. Adware comes bundled with some programs to keep product costs low, and publishers notify users they are installing it in the program's license agreement. However, many people don't read license agreements, and aren't aware that they're giving away their personal information.
  
  

Malware

• Malware is software developed for the purpose of harming computer systems. Viruses, the most well-known type of malware, spread across computers by attaching themselves to the system's programs and documents. Worms and and trojan horses are other examples. Although each works in a slightly different way, they all make changes to your system, sometimes deleting files and making your computer impossible to use.
  
  

Spyware

• Spyware is a more insidious version of adware, collecting personal information without any end-user notification. Spyware programs are usually independent programs bundled with other software. According to Spyware-Removal-Info, spyware can scan hard drive files, record keystrokes and monitor application use, sending information back to the author, who uses or sells the data for marketing purposes.
  
  

Preventing Infections

• Never open files from an unknown source, and avoid downloading freeware. If you must download a free application, read reviews critically and ensure that you understand the end-user license agreement. Keep your operating system current with the latest patches and fixes.
  
  

Detecting and Removing Infections

• Make sure that you have updated antivirus software and that you scan your computer regularly. Microsoft Security Essentials and AVG both provide effective, free protection against threats and can remove malicious, snooping software from your system if a scan detects it.