Spurious: counterfeit; false; bogus; not proceeding from a true source.

Spurious writings are not composed by the authors to whom they are ascribed.  With new technologies, it is sometimes difficult to determine authentic writings from spurious writings. 

Politicians often accuse each other of being spurious.  Of politicians, Mark Twain once wrote (not spuriously): “Politicians and diapers need to be changed often and for the same reason.”