Last few days exchanges like Cryptopia and Coinsmarket are down, Maintenance or something else?

Hi, im very fresh to Steem and in crypto in general and would really like your opinion, for the continuing block on trades in Coinsmarkets, Cryptopia and other. Is it just a coincidence and regarding maintenance issues, or these sites are often under some sort of attack? In the later case how safe are the wallets in there?
Thanks

George P
GPDesignlab