Security measures for smart phones are important. Anti-virus software for smart phones can be used and the process consumes CPU resources. The CPUs of them are powerless CPU for an embedded system and those operations consume battery power. In this paper, the authors propose packet filtering circuits for smart phones. The packet filtering circuits are a firewall. Using the firewall is a means to protect smart phones from computer viruses and unauthorized access. In addition, they are used to control the power consumption and to reduce of detecting units for unauthorized access. The features of the circuits are to achieve those functions without reconstructing circuits. The operations of the circuits are verified by gate-level simulations.
