Malware - short for malicious software - is an umbrella term that refers to any software program deliberately created to perform an unauthorized and often harmful action.
Viruses, backdoors, keyloggers, spyware ,adware, rootkits, and trojans are just a few examples of what is considered malware.
A few years ago,it was once sufficient to call something a 'virus' or 'trojan horse', however today's infection methods and vectors evolved and the terms 'virus and trojan' no longer provided a satisfactory definition for all the types of rogue programs that exist.
Free programs now have become one of the major channels spreading Potentially Unwanted Programs (PUP), Adware, Spyware and Browser Hijacker. Usually, when you download and install free programs on third party websites, some threats like Websteroids is installed without your knowledge if you select the “typical install”. To protect your PC from unwanted and harmful programs, it’s best to choose “custom install ” when you install free programs, and you should Uncheck all the boxes which prompt you to install bundled programs.