A method for preventing network attacks is provided, which includes: obtaining a data packet, where a source address of the data packet is a cryptographically generated address (CGA); determining that the obtained data packet includes a CGA parameter and signature information; authenticating the CGA parameter; authenticating the signature information according to the authenticated CGA parameter; and sending the data packet to a destination address when the signature information is authenticated. Accordingly, a device for preventing network attacks is also provided. A CGA parameter used by a data packet is directly used to ensure authenticity of a source address of the data packet, thus preventing network attacks performed by counterfeiting the address. In addition, by authenticating signature information, authenticity of identification of a sender of the data packet and bound address of the sender of the data packet are further ensured. Therefore, illegal data packets are filtered to prevent network attacks on servers, thus improving network security.