Spyware is a type of malware designed to spy on the victim's computer activity and report it to another computer over the Internet. Spyware can capture information like Web browsing habits, e-mail messages, usernames and passwords. It generally does not harm files or applications since its goal is to remain undetected as long as possible while it gathers and transmits data.
Hackers that deploy spyware are often interested in information they can use directly, or that is profitable to sell to a third party. Some spyware is designed to steal information that could be used for identity theft or other financial fraud — bank account login information, personal data, and cryptocurrency wallets. Other types of spyware merely monitor computer activity to inject advertisements into webpages. Some hackers deploy spyware to target a specific person known to the hacker, often to monitor the victim's online activity and physical location in cases of stalking.
There are several methods that spyware can use to monitor a victim's activity. Keyloggers are a common component of spyware, recording every keystroke a user makes to intercept usernames and passwords. Spyware often tracks a user's web activity, much like cookies do. Some spyware can also capture images and video recordings of the user's screen; some can even control a computer's microphone and webcam. While some spyware gets installed through an exploit in a web browser or operating system, most spyware is installed by the victim unknowingly in a Trojan Horse or included with legitimate-looking software. Fortunately, antivirus software can catch and remove most spyware.