TCPDF error: Unsupported image type: net/image-2591334-10411368 Sitemap Performance of ZoneAlarm Free Antivirus + Firewall is very good. Quick scans take only a few minutes. Full scans will take some time but are still an improvement over older ZoneAlarm programs. The speed increase is a result of a redesigned scanning engine. Still, we found ZoneAlarm Free Antivirus + Firewall to be resource intensive on our system and slowed our boot times down. Competiting antivirus applications were quicker and less resource heavy.