There is fraudulent art selling all over the place. You can't swing a cyber cat by the tail without hitting a site selling "stolen" work.
You can attempt to be vigilant, but if someone wants your work badly enough, they will take it.
This was going on long before the internet. In the early 80's I worked for a guy that had galleries of "original art" We went to an old warehouse in Brooklyn and would order hundreds of imports. We ordered them by "artist" I remember I liked Gordon who did seascapes. Or he would order by subject. The captain and the boy was popular. So were clowns. Each was original but based on a Western painting. Probably 3 or 4 artists worked on each one. One might just do seagulls in the sky. The brush strokes always had an Asian look. Most were from Hong Kong then. I had heard some also came from Mexico and the Mid -East. I guess they would forge to order then also. I wouldn't lose any sleep over it.
