Crypto exchanges algorithms I have noticed that if I put a buy order up - for instance - on any not so heavily traded coin, if close to the highest bid, often within 20 secs the highest bid will try to beat me.
Or when I put it close to the lowest ask price, often it won´t take long till I get someone to sell it to me. 
Before this there can have been hours with no activity.
To me, this does not look like bots that are set up to track MDA or other common strategies, but the exchanges own bots reacting to certain inputs.
Does somebody know more about the algorithms used by the crypto exchanges, which behaves this way?

Thanks in advance!
you're providing alpha to "high frequency market makers". Since they can tell that you are not a bot, they are assuming its a real bid, so they can bid on top of you and then they are now in a risk free position. 

if they get hit, they will immediately place an ask at a price of:  last + (last-bid). they will wait hoping you will pay up, they may even entice you by placing another bid higher... then (within a couple of seconds) they will hit your bid, and take the small loss. 

as long as the spread is much wider than the tic above you, they are in positive alpha. 

in general, you should not try to play this game. just place "marketable" limit orders.. so buys at the best ask, and sells at the best bid, otherwise you are giving away your hand.