One doesn’t need to be a forensic analyst to know that every single transaction is tied up to addresses on the blockchain and that they will stay there forever.
Bitcoin mixing services such as Bitcoin Fog allow users to mix their coins with other users, making it almost impossible to detect the destination addresses.
Mixing services are offered in a wide range of methods, including fully centralized solutions where trust is required, to Coinjoin mixers, which depend on a large group of users to self cooperate and act simultaneously.
Centralized mixers offer the obvious single point of failure problem.
The service will then take those coins, craft them into a transaction, and have each participant sign before broadcasting it to the network.
Even though CoinJoin isn’t exactly untraceable, it provides plausible deniability, as no one can point out which entity owns each output.
A similar service is provided by Samourai wallet, which also offers a Chaumian CoinJoin mixing service, called Whirlpool.