How to remove “Your Mac is heavily damaged” scam message

“Your Mac is heavily damaged” is a fake alert that might show up on your browser screen and its appearance is the main sign of infection with malware. This message aims to trick users into believing that their system is infected and they need to download specific removal tool (Mackeeper or Advanced Mac Cleaner). It is quite ironic since these are fake programs that do nothing but display fake system issues to correct which demand the payment.