Malware
Software intended to damage or disable a computer system
Malware can appear as just about anything, even an anti-malware website. Most commonly it appears as an unusual screen or webpage that pops up. They may ask for personal information, such as your credit card number. A person can avoid getting malware by not clicking on ads that appear on any website. Check what you download, and look for unusual domains, as these are an indicator to if the website is infected.