They aren’t unfortunately, as its very hard to make a filter at such small levels catch all the particles, often it can only choose between 2 types of particles, large medium and small. N95 masks get around this by making the material charged, so they catch large and small particles, and the static charge catches the medium, and that’s providing you have a good seal. so these masks which don’t use that technology just don’t work for the purposes of viruses, they work for certain bacteria, which is how this all started.
to make it worse the simple masks become a casino for other bacteria, mould and viruses most of which are harmless but some defiantly aren’t.