For a free antimalware and antivirus app that also runs in your system's background, AntiVir works surprisingly well. Its scans are flexible, allowing the user to fully scan all hard drives, choose a preloaded scan--for rootkits, for example--or customize a scan. Combining the antimalware with the antivirus is a luxury in a free scanner. After testing on several machines no viruses turned up, although several malicious hidden files did rear their heads. The heuristic scan can be turned on or off completely or partially, with three different intensity levels.
The quarantine is extensively thorough, too. The spreadsheet layout displays all relevant information about the quarantined file, and gives you options to scan it again, restore, delete, and more. The scheduler is fully customizable. Definition files are available at Avira's Web site if needed, and the help features are excellent, as well, with a description box relaying mouse-over information on each feature. Version 8.0 has introduced a faster engine and a faster definition file update, both of which are instantly noticeable improvements and yet still a bit slow.
Initial concerns about the real-time Guard protection hamstringing system performance proved groundless. Although we could shut off AntiVir and its Guard, there was no way to remove the icon from the system tray or stop the occasional ad placement by Avira. The Complete Scan is no longer numbingly slow, but it will pauses midscan to let you know when it's found a threat. That's good for killing nasties, but it also means that the scans needs baby-sitting.
Despite these hang-ups and the nag screen that follows updates, we found AntiVir to offer such effective protection with such a well-rounded set of features that as long as the definitions file updates keep coming, this app is our first line of defense.