Contrary to popular belief, blockchain technology does not guarantee user anonymity, but quite the opposite, leaves transactions in plain sight. Tracking the movement of the same bitcoins is not at all difficult - and for this you do not have to resort to spyware methods. It is logical that in such conditions, the world has its own methods of hiding information and "laundering dirty cryptocurrency".
The simplest and conventionally accessible method for anyone is to use "mixers" or "toggle switches" in slang. Usually they are presented in the form of some kind of interface on the site on the darknet, although in fact it is not a mechanism, but a chain of actions. Bitcoins are transferred to a dedicated wallet, where a special algorithm splits them into fragments and sends them to several other wallets, applying masking through the Tor system. The size of the fragments, the interval between sending, the address - everything is determined by chance, once in history, so it is extremely difficult to track where these crumbs of bitcoins were scattered.
These fragments, fractional parts of bitcoins, are transferred through several wallets and, as a result, are collected again in the resulting account. The amount in bitcoins there will be exactly the same as initially, minus the commission for the service, but it is almost impossible to trace all the chains of transactions. Those who do not want to blindly entrust their cryptocurrency to "laundries" are advised to simply create several accounts on any of the major exchanges for exchanging virtual money. And then, selling yourself bitcoins with conversion into other "coins" and vice versa, you can try to confuse your tracks.
Alas, in reality it all depends on how carefully the unspoken rules "Know your customer" and "Anti-money laundering" are followed by the administration of a particular service. And Interpol data suggests that 97% of all laundered cryptocurrency immediately goes to the darknet to pay for clearly criminal services - for which it is laundered. No one will give any guarantee that the chosen site will not be tricked, and the information will not be resold - to the mafia or the police - for an official reward. In 2016, the Dutch police in this way exposed a large international network of "laundries", arresting numerous luxury supercars, bank accounts and luxury goods in addition to cryptocurrency.