What you can do is simply prevent access. You need to evaluate your child, if he is the type to bypass the internet filter, than he shouldn't have access to said internet.
This is the logic that people have been spewing from the first page of this thread. Its astonishing. You want to give parents full liability for what their child does even though it may go beyond what's reasonable for a parent to know or look into yet want absolutely no blame to be placed on criminals who scam people (children or otherwise) out of money.
How does this outlook reflect on you people's opinions on other stuff? Will you blame yourself for getting mugged? For getting run over by a drunk driver? Are these people who run sites that would be illegal in any country with law enforcement so innocent to you?