How did Liu Jianming’s text message get sent?

Anonymous. Liu Jianming is a character in "Infernal Affairs". The text message "There is a mole, terminate the transaction" was sent anonymously. Liu Jianming grew up in a housing estate and joined a bad organization when he was young and ignorant. Later, he accepted the instructions of the social eldest brother Han Chen and joined the police force and became a senior inspector of the Criminal Intelligence Division. Han Chen responded internally.