Of course there are measures that the SM crew can adopt, and imo should adopt.

1st Cancel temporary the game's credit system. I know that this is though but is important to avoid this, could happen again.

2nd They should talk with a lawyer, if this is a crime and all the clues indicate it, they are concerned and should inform of what happened to the authorities. Colaboration with them means that this kind of behaviours aren't allowed in the game.

3rd Limit the card prices for types, for example 1$ for a common 5$ for a rare 10 for a epic and so on...

4rd Try to implement some measures to control the use of the Credits, and try to maintain the DEC price with some stability.

These are some measures that they could take, I'm sure that the staff will have ideas like these or better, but the issue is to take action and don't wait and see what happens. This attitude could be taken as some kind of acceptance with fraud, and crime.

Ty for the post @jrvacation, very interesting info.