Avast is malware. It may remove other malware on your computer but Avast itself is also malware. It sends your personal data out to remote servers even when privacy settings are selected. It is popular because it is free. It is free because obtaining your data is profitable to them. If you install this software with a default installation, every website you visit is streamed to Avast. Along with data from the content of the file scan of your computer. If you install this software and choose not to send out your data in the preferences, it stills sends your data out. This is how they operate.