Various forms of advertising, including additional toolbars, homepage hacks, and data insertion (while technically not a form of spying) are often also included in the term to determine the presence of spyware.
Virus detection is more typically data-based, looking for specific patters of data that indicate the presence of a virus.
Recent versions of Windows include a built-in software firewall.
Spyware is a class of malware that, as its name implies, is typically designed to spy on you or your computer, silently collecting information that is subsequently sent on to others for typically nefarious purposes.
What’s important is that it continues to have a very good track record of removing troublesome malware that other packages sometimes miss.
Spybot Search and Destroy is one of the longest running and highly regarded anti-spyware tools out there.
Like Malwarebytes, it has also expanded to be a more fully-featured anti-malware tool.
These devices not only allow multiple computers to be connected to a single internet connection, but they act as a type of firewall, protecting against malicious traffic from the internet.
There are also dedicated hardware appliances that act only as firewalls, and there is software that can be installed on PCs to act as a firewall as well.