The recommended procedure is to use a different receiving address each time you receive funds. You have a couple of scenarios where people could find out:
1. If you send bitcoins from one of your addresses to another on a regular basis, one could come to the conclusion that you control both addresses.
2. If you receive funds in different addresses (0.5 BTC in X address, 0.5 BTC in Y, 0.5 in Z) and then send 1.5 BTC to another address, the blockchain will show that the funds came from these three addresses and so people will know that you control the three of them.
However, If you just create an address like you said and you're not really doing anything, then no there is no way to know unless they have your wallet.dat file.
That's the answer I was looking for, thank you! If I had merit I'd have given it to you
Thanks again!
Or if you use the same "change" adress for multiple adresses.
Say you make a transaction using adress X worth 1 BTC, whereas adress X holds 10 BTC. 9 will go to "change" adress Y.
Let's say that adress Z also holds 10 BTC, and you spent 1 BTC of it, where, again, 9 will go to change adress Y, more or less connecting both of the adresses.
I doubt this is common practice in most wallets nowadays anymore, but you should always make sure you use different change adresses correctly if you want some extra privacy.
