I've had this cactus for about two years now, and this winter in began showing these white, flat dots that look like splattered paint. They can be scrapped off, but there's no sign of an insect or anything moving. They also don't have the typical red dye of cochineal bugs, nor the fuzzy texture. The cactus receives plenty of light, though not direct sun, and has for sure not been over-watered. The dots seem to be spreading fast through-out the leaves, but thankfully other cacti that I have, have not been affected.
I have tried scraping them off with a toothbrush, but I don't think that will get rid of them for good.
Any ideas on what this is and how to get rid of it would be greatly appreciated.