A packet processing method. A protection device receives a first access request packet. The first access request packet includes a packet sent based on a TCP/IP protocol. The protection device extracts a first fingerprint feature from a transport-layer packet header and/or a network-layer packet header of the first access request packet. The first fingerprint feature corresponds to an operating system type of a terminal device that transmits the first access request packet. The protection device recognizes the first fingerprint feature based on a fingerprint feature database to determine whether to allow the first access request packet to access a server. The protection device allows the first access request packet to pass through when the first access request packet is allowed to access the server. The protection device blocks the first access request packet when the first access request packet is not allowed to access the server.