This is a prophecy that comes from the rabinical traditions of the Kaballistic Jews and appears to have several points of origin.  However, the most likely is that of Samson ben Pesah Ostropoli of 17th century Poland.  The prophecy itself seems like a twisting of Ezekiel 38 with it accurately carrying some facts (ie, Russia's invasion of Israel) but then fails in other points such as the idea that Russia will conquer and subdue Israel, even though Ez38-39 says they will only make it as far as the mountains of Israel (likely somewhere in Judea) and will be soundly defeated and destroyed there.  This prophecy suggests that, instead of being defeated, Russia (Gog) will successfully conquer Israel.  Thus, since it's in disagreement with the bible, it's automatically false.