The embodiment of the invention discloses a network access method, device and system. In the embodiment of the invention, after a network access request sent by a terminal is received, identity verification can be carried out according to the network access request; furthermore, when the fact that identity verification is successful is determined, whether key interaction information of the terminal and the home terminal exists or not is determined; if so, the access is a normal access behaviour; if not, the access is a malicious behaviour; and the network access request is refused. By means ofthe scheme, the malicious login behaviour can be effectively identified; and thus, the information security is greatly improved.