The idea that any cryptocurrency transaction is private by default is a common misconception. In fact, the opposite is the case. Blockchain data is public and transactions can be tracked. Cryptocurrency mixers and privacy coins were created to bring privacy to this open financial system.
In short, mixers are simple but efficient services that help users hide their fingerprints on the blockchain. However, they are very unreliable and users may face legal problems if they ever use them. You can use a centralized mixer, which are third-party services that receive bitcoins, extract other bitcoins from other deposits and return an equivalent amount of bitcoins at the end of the transaction. However, Chainalysis noted in its report that it is “not aware that any bitcoin or Ethereum mixer is currently following these rules.” According to a July report from Chainalysis, cryptocurrency mixers are a “reference tool” for cybercriminals who trade cryptocurrencies, and illicit addresses account for nearly a quarter of the funds sent to mixers since January.
Mixers and glasses slow down that process and hinder progress, but that's not always the end of an investigation into cryptocurrency tracking.