This is probably one of the easiest questions to answer but it isn't enough to give an answer without taking one through the process.
The answer to this question is simply to follow decentralized protocols, but just throwing that out there without acknowledging the flaws of it and how that might not be sufficient would be insulting to those truly looking for answers.
I mean, let's face it, there's a real crime problem, the politicians definitely over-exaggerate when it comes to current impacts but we cannot ignore that in the long-term, it can be an economic-level threat.
Most illicit funds today flows through traditional systems because that's still the most effective option, when all boxes need to be checked.
But as finance moves on-chain and privacy tech gains momentum, we could find ourselves in not so pretty situations.
Safeguards
The first thing to address is safeguards. How do we protect what we already have. There are several levels of crime, but we have to begin with exploits or hacks.
How do we limit how bad actors can steal from others and get away with it?
Again, this is also easy to answer.
When it comes to safeguards to user funds, we are mostly dealing with smart contracts security and personal security measures.
One is generally out of the control of external bodies, individuals will need to take charge of their funds security through education and application.
That said, when it comes to smart contracts security, I expect that this an area where active developments to improve are ongoing.
But this isn't something I wish to address here.
World altering crimes
Small hacks and scams here and there don't really move a needle.
Fact is, even when worth several millions or billions, as much as value is exploited, it isn't in itself the biggest problem of permissionless networks.
The real crimes that we ought to care about are ones that could alter world order.
We are talking about terrorism financing and funds flowing into world governance systems.
The fun part is that governance and terrorism is in the same department.
So how do we fix that?
How do we fight such crimes on-chain?
I think the solution here is that governance has to move on-chain.
Being that these crimes are mostly governance-facing. Fighting them demands a revamp of what nations governance should look like.
Privacy tech isn't the problem. Having finance run on permissionless layers isn't the problem. The problem is the governance system itself.
It needs more transparency and more power ought to be moved back to the people and that can only happen by bringing it on-chain.