There are a plethora of illegal books, many run by college students, young adults and even teens. How secure are these websites??
What I am really asking is how easy (possible) would it be to hack the site and change a users balance without being detected??
You do not need to gamble on these illegal sites to enable you not fall victim to their scam. Gamble in a reputable casino that you know nothing will deprive you from withdrawal of your funds when you win big, and there will be no excuses.
Those incompetent people operating the illegal site, are up to something, if not why will they operate in an illegal way. It is good that you stay away from them, because they are not doing the right thing, and every other aspect of their site and activities will not be real.
I don't know why someone would see that a site is operating illegally and still prefer to gamble there, in the first place.
Such sites can't assure you to get your winnings if you do win big and we even see how the registered and legal ones fail to remit wins or give rewards or respond to customer's grievance on time, let alone an illegal site doing same, unless you know the host and it's a closed group of gamblers and you understand the risk involved.