According to a support page on Rockstar’s website, the company published a Q&A regarding cheating, in which accounts that are found cheating for in-game cash will have that cash removed. Rockstar writes, “To keep the gameplay environment fair we have removed illegitimately gained in-game money from player accounts. If you received an alert saying that your shared bank balance was adjusted, that is because you had illegitimate funds in your account.”
Note that this only applies to any cash that players have obtained illegally, such as through cheating. This means that any cash that you have earned legitimately such as through Shark Cards will not be affected, but everything else will. The good news is that it seems that the removal of cash is all there is and that cheaters will not have their accounts banned, as you can see in the screenshot above posted on the GTAForums, something that other developers such as Blizzard have been very aggressive about.