Recently my computer was attacked by different kinds of worms and my computer was slowed down. So I tried to remove them by installing Avast free antivirus. The worms were copying themselves rapidly. But after installing avast, I observed it only blocked new copy of the worms to be created but could not delete the already created worms, even it could not find worms in a good amount. Then I downloaded Malwarewbyte Anti Malware and to my surprise I found out its service was way too better than Avast antivirus. It detected and deleted almost 2065 worms and malwares from my computer and now my computer is doing fine. As far as I know, anti malware functionality is also included in Antivirus, But then also its performance is poor. Now my question is if performance of antiviruses are meat to be poor than Antimalwares, then why the size of Avast is 179Mb and the size of Malwarebyte is 9.81mb?