The detection and characterization of explosives, of their taggants, or of their degradation products is a topic of crucial importance for public safety. It undoubtedly plays a key role in luggage screening and bombing scene investigations. At least two challenges need to be addressed by high-resolution spectroscopic techniques: the detection limit should be better than 1 ppb and the discriminating power should allow to unambiguously identify chemical species despite of similar properties. The direct detection of classical explosives is out of each for most spectroscopic techniques due to their extremely low vapor pressure at room temperature. Alternatively, they can be applied to the detection of explosive taggants which are intentionally added to explosives or found as impurities due to the manufacturing process. We present here the study of dimethyl ditro butane (DMDNB), a detection taggant for explosives largely used in plastic explosives. The microwave spectrum (2-20 GHz) was recorded with a free jet Fabry-Perot Fourier-transform microwave (FP-FTMW) spectrometer and line frequency analyses were carried out with the support of quantum chemistry calculations. The spectroscopic parameters determined for the most stable gas phase conformation include the effective quadrupole coupling constants describing the hyperfine structure arising from the two 14N nuclei. The cavity-based mm-wave spectrum (150-215 GHz) recorded at room temperature shows features that belong to the two other possible gas phase conformations. Their analysis is in progress.