Hacking a blockchain is somehow impossible, don't worry about that... There are many accounts like @null that are used by the system for many different things...
BTW, don't use those whale and booster thinks for now, they are not worthy, as the steem price is low and the pool is draining, your payout will decrease, so any "boost" you could get from those bots are going the get lost after the 7 days ends...
Minnowsupport is the only good bot that doesn't charge you anything, use that one!
I was realizing this too, So if i understand well we should wait until steem price rises again in order to use this accounts in a more profitable way right ?
Yep pretty much... But honestly i don't think there is a real profit in using those paid bots, they continuously decrease their voting power in order to vote more post and earn more money, so each post will get less payout, they don't care about giving you poor payout... Those bots are business, but you can use minnowsupport which is a real minnow helping trail with not monetary interest...