[bisq-network/proposals] Delay payout for Fiat trades if buyers account is fresh (#77)

Manfred Karrer notifications at github.com
Sat May 4 15:12:41 UTC 2019

I think it depends on the amount on an account and the cost for the scammer to get access to it. 
There is some risk that the victim or bank detects it even with small amounts. Of course we don't know number but from what we have learned in the past weeks we could try an educated guess.

The scammer had used about 14 accounts but only could cash out mainly 2 accounts (and 1 or 2 others with one tx). His gain was about 11 000 EUR in total. To be profitable he must not pay more than 1000 EUR per account (will prob. depend on the amount in the account). He lost also some Bitcoin in deposits once he was detected. He got detected after about 1-2 weeks so he needed to do it fast. Liquidity on Bisq was probably one natural protection as he probably could not cash out in 1 day all. Cashing out a lot very fast might trigger also bank-side protections as un-usual behaviour. They monitor clients spending behaviour and detect such things (I assume). So cashing out one account with many fast trades is very risky for him. The number of transactions is likely an important factor increasing his risk.

So lets think through a potential scammers strategy to exploit our protection:
Lets say he got 20 cheap accounts with costs about 200 EUR (total cost 4000).
He starts with small sell trades to get attested with all. He need to wait one months and then can cash out 0.125 BTC per tx (about 600 EUR). If he suceeds he has gained at least 400 EUR (600-200). So if he has 50% sucess rate that the sell trade kept undetected he would be break even.

Of course lots of uncertainties and unknowns in that model, but just trying to get a bit better an idea from his position. 
We saw that with his 14 accounts he was only successful with 2, so detection rate at banks seems ratehr high. Of course receiving money might be less easily detected as spending. Specially spending small amounts I think is monitored well as there might be scam schemes where they try to make many micro transactions in the hope the victims don't notice it. 

So it seems that the detection rate at banks is a main factor we need to consider. With that in mind restricting attestation to buy offers only would probably add substantial secruity. 

I think the first trade will be mainly a kind of "validation trade" where he starts to get attested. If the user buys or sells here a small amount is probably not that relevant, buying seems even more logical as new users might be Bitcoin newbies wanting to get in Bitcoin. 

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