A packet filtering method, system and article of manufacture are provided which include: employing an instruction set associated with a pseudo-machine in filtering packets received at a network interface card coupled to a host, wherein a set of instructions of the instruction set implements at least one byte-defined filter rule; and the employing includes for a packet of the received packets, processing bytes of the packet as a bytestream and applying at least one filter rule to the bytestream to filter the packet. The applying can be performed in any one of a plurality of locations without customization of the instruction set, including the network interface card and the host processor coupled thereto.