Malware is a blanket term that is used to describe a number of malicious types of software, including adware, spyware, viruses, trojans and more. Spyware is a specific type of malware, but is quite different from most other malicious software because of what it is designed to do.
Most malware is designed to cause harm to your computer in some way. Many programs can damage your computer by accident, but malware's sole purpose is to cause errors, slow your computer down or spread viruses. Spyware's purpose comes from its name, and is designed to watch your actions. Spyware will look at what sites you visit, and in more extreme cases, track what you type to steal your passwords and personal information.
Malware like viruses and trojans will generally just cause problems with your computer itself, such as slowing it down or causing errors. Spyware collects your personal information, and can therefore cause much more long-term damage by giving other people access to your online accounts, bank information and more.
Trojans, viruses and similar malware can be transmitted in a variety of ways -- from the websites you visit, programs you download and emails that you open. Because of this, they often have more points of entry and can more easily infect your system, and prevention entails using a firewall and making sure your antivirus program can work in the background to detect them automatically. Spyware can be a bit more tricky to detect, and it may infect your system without your knowledge. Antispyware programs are more effective in the removal stage, rather than for prevention.
While most malware can be scanned for and removed by an antivirus program, spyware is a bit better at hiding itself. To remove spyware, an updated antispyware program usually does the trick; antispyware programs are different from antivirus programs, so it's helpful to have one of each on your computer. Antispyware programs also generally do not monitor your computer, and may only pick up spyware during system scans.
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