Speaking To the Senate Armed Services Committee on April 5, 2016, Admiral Michael Rogers, head of the military's Cyber Command, said that while Russia and China still present the greatest cyber-security threat to the U.S., Iran is trying to increase its capabilities in this field.
Admiral Rogers said that while the U.S. has more overall military power than those three countries, the gaps are narrower with regards to cyber-warfare.
Additionally, Defense Secretary Ash Carter order to beef up use of offensive cyber-warfare in Iraq and Syria, and made the increase of cyber-capabilities a key goal of the DoD.
Source: Gadgets.ndtv.com, April 6, 2016.