In this paper, we presented vulnerabilities and countermeasures for em- bedded processors. Among all kinds of vulnerabilities and external attacks, we are most interested in power attacks, which infer program behavior from observing power supply current into an embedded processor core, are important forms of security attacks. In this work, we addressed a novel approach against the power attacks, i.e., Dynamic Voltage and Frequency Switching (DVFS). Results showed that this method hides processor state with 27% energy reduction and 16% time overhead for DES encryption and decryption algorithms. Furthermore, system leakage power, as an obstacle to power attacks in the future technology, was studied. Results showed that leakage power scaling makes the power analysis really difficult to be carried out and leaves crypto embedded processors secure without any kind of overheads.