In order to track suspicious transactions exchanges mainly use third-party solutions to streamline their AML processes. The most popular solutions are Chainalysis, CipherTrace, and Elliptic. They are used by regulated exchanges and exchangers - as well as law enforcement agencies. There is also a built-in AML check in the BitOK crypto service. It checks transactions for dirty crypto and notifies users if it finds it.
According to the AML directive cryptocurrency from the FATF, all countries had to introduce rules preventing money laundering using cryptocurrencies into their laws in 2020. In addition, leading Western countries are carrying out AML crypto enforcement action. The basis of these actions is to confirm the identity of the user so that through it it is possible to track the transaction history of a particular coin. AML in traditional financial services uses data about the identity of the owner and does not require knowledge of all transactions within the system for enforcement. The Bitcoin ecosystem, in contrast, provides regulators and law enforcement with anonymous wallets that are not easily linked to identified individuals, but at the same time, the blockchain offers the police a complete picture of every transaction made in the system.
However, some jurisdictions and exchanges do not regulate the purity of coins in any way. There is a huge dark market for transactions where users exchange compromised tokens in parallel with the usual one. These are not always criminal operations: many crypto users just want to maintain their anonymity. For an ordinary user anonymity and crime are the same in this case. If you are a law-abiding user you shouldn't make transactions in this field. Such transactions carry only risks for you and no profit.