We developed a method to compute Raman and Infrared frequencies of nanostructures of arbitrary dimension. Our method is based on molecular dynamics simulations and a symmetry analysis of the structure of interest. The calculation of electric properties like the polarizability and dipole moment is not required, which makes our method usable with existing molecular dynamics software. Raman peak shifts for bulk silicon were calculated for different temperatures and lattice constants and showed good agreement with experimental observations. Additionally we calculated the dependence of the Raman peak shift of silicon nanowires on the wire diameter and on surface stress.