Which FOSS video editor did you find?
/dev/fb0 is the framebuffer. So yes, you can feed data into the filesystem and you’ll see it on your display.
For Unixoids, being a file does not mean that this data is stored on a hard disk, but that all data, processes and hardware are accessible with the same toolkit. /dev/fb0, for instance, is part of the file-like interface of your graphics card.
AFAIK, clamAV hunts Window viruses, not Linux malware. The linux equivalent I know of is rkhunter.