How much do the Russians know?
Alot? Kinda of a big question there. The Russian have made many mistakes but you don't go toe to toe with the US for 50 years being stupid.
Given the, um, uneven track record of the Patriot missile interceptor, you'd think such a weapon might not be necessary. But Russia has gone ahead and put together "the first ballistic missile ever to include built-in countermeasures against the West's growing range of deployed theatre missile defence systems," according to Jane's Defence Weekly.
The Iskander-E short-range ballistic missile is designed to defeat Western ballistic missile defence systems, particularly the Patriot air-defence system...
It appears to forego conventional chaff, flare and anti-radar signals and instead employs manoeuvring at both launch and attack phases, a low and direct trajectory and a low radar signature produced by what Russian reports called "a special composite"... These details will be [puzzling] to Western missile defence specialists.