Methods and apparatuses providing file type inspection in firewalls by moving the flow between deep inspection file and lightweight accelerated paths. The method includes obtaining, by a network security device, a packet flow of a file transfer session in which at least two files are transferred and determining, by the network security device, at least an offset parameter based on at least one attribute of at least a first packet in the packet flow. The offset parameter is for a first file being transferred of the at least two files and relates to an expected positon of a control data sequence within the packet flow. In this method, based on the offset parameter, directing, by the network security device, to an accelerated packet inspection path instead of to a deep packet inspection path, a portion of the packet flow including one or more packets that follow the first packet.