Anti virus is a essential software which keeps you safe from being exploited. Computers or mobiles or any other electronic devices are venerability without anti-virus software.
There are many anti-virus softwares available for free on-line and some are to be purchased. My favorite anti-virus softwares for computer are AVG technologies, "Avasta", "Kasparskies", "Avira", Windows Defender, and some anti-virus software for mobile phone are "avast anti-virus security" and "AVL" .