Answer : BitDefender Antivirus Free Edition is one of the best free antivirus programs , as it does not use much system resources to block the deadly threats. BitDefender Antivirus Free Edition on Demand is not a virus scanner. This BitDefender Antivirus Free Edition does not need to be ' turned on' or started every time to check for malware , since it runs all the time. BitDefender Antivirus Free Edition continues to provide virus protection , called on-access or resident protection. This means that, according to McAfee and Norton, antivirus software companies charge an annual fee for access to their software. BitDefender Antivirus Free Edition replaces them completely.