Robert Moskovitch Dima Stopel Clint Feher Nir Nissim Yuval Elovici Unknown malcode detection via text categorization and the imbalance problem. 156-161 2008 ISI http://dx.doi.org/10.1109/ISI.2008.4565046 conf/isi/2008 db/conf/isi/isi2008.html#MoskovitchSFNE08