Are there undercover policemen in reality?

Undercover police do exist in real life. Undercover police usually go deep into criminal gangs, collect criminal evidence and crack down on criminal activities. They may sneak into the police station for a long time, or infiltrate into large criminal gangs, such as drug gangs and robbery gangs. This kind of work is very dangerous, because the criminals that undercover police need to face may be very cruel. Once the identity of undercover police is exposed, their lives may be in danger. Undercover police are an indispensable part of police work, and their work is of great significance for maintaining social order and cracking down on crime. Undercover police is another name for the police who have sneaked into criminal gangs for a long time. It is a special police set up by the police station to help solve difficult or major cases.