Patent ID: 10110557

Abstract:
Disclosed is a method for Application Specific Packet Filter (ASPF) of a File Transfer Protocol (FTP), including the following steps: when a Transmission Control Protocol (TCP) connection of an FTP control channel is established, a first TCP Synchronous (TCP SYN) packet sent by a client is obtained and forwarded to an FTP server; it is detected whether a response packet from the FTP server is a TCP Synchronize-Acknowledgment (SYN+ACK) packet, and if not, the response packet is discarded; it is detected whether a response packet from the client is an ACK TCP packet, and if not, the response packet is discarded; and a data flow table is created to record and update an FTP state. A device for ASPF of a FTP is also provided. The method and device can avoid and stop the attacks from the FTP application layer, and ensure safe and reliable transmission of an FTP service.