Malware refers to malicious software that tries to infect devices without the user's knowledge. It comes in many forms like viruses, trojan horses, and ransomware. Malware most often gets onto devices through the internet, email attachments, or downloaded files. Signs of malware include slow performance, pop-ups, spam, and crashes. The best way to remove malware is with reliable anti-malware software, which can quickly scan and clean infected devices. Using antivirus software and safe downloading practices helps prevent malware.