In Syria, the Russian military repeatedly attacked US aircraft, both combat and reconnaissance. This is stated in the report of the American Institute for the Study of War. True, the document immediately states that the air defense of Russia does not bombard the US aircraft, but uses electronic suppression systems in relation to them.
According to the document, in the SAR Russia is testing new electronic combat systems. According to intelligence from the US military, in Syria, Russia has deployed at least four unique electronic warfare systems. And they are used very, very specifically. Russia uses them to stop US military operations against ISIS (a banned organization in Russia).
Moreover, Russia almost every day either monitors or disrupts communications between the US military units stationed in Syria. And according to the authors of the report, the world is on the threshold of a new to the village of unprecedented electronic war, which, of course, Russia will begin.
However, there is one nuance. Regular troops of Russia are the only ones who stay in the country with the permission of the majority of its population. And the UAR leadership welcomes and fully approves the actions of the Russian military in the territory of the Syrian Arab Republic.