4.) Russia 

Russia was famously accused of hitting the US with cyberattacks in 2016, while many of these allegations were proven to be untrue the country did attempt a disinformation campaign within the country that sadly succeed. This does not discredit the notion that Russia actively seeks to attack the US through cyber warfare though when these conflicts arise it is important to hit back just as hard. Due to the nature of this kind of warfare, it will likely be some time before the larger population knows exactly what happened.