Malwarebytes Anti-Malware. You know that viruses are bad for your system, but they are just one type of malicious software. Broadly speaking, malware is any software developed to disrupt your computer or device's normal functioning. Malware is often used to steal, to spy, or to destroy. It can target your personal information, corrupt your files, spam your contacts, use your computer for nefarious purposes, or even render it useless.