Russian air defense systems are notoriously bad in terms of their performance against ECM. This is not necessarily because of a fault with the Russian systems, but may be caused by a wide range of activities.
The top ones ottomh could be:
- The Americans and West has always trained and developed their weapons systems to counter Russian equipment and doctrines, so its hardly unreasonable that they are particularly effective against Russian systems.
- Russia has not been all that picky about who they sell their weapons to. This has resulted in the US (and Israel in extension) gaining first hand access to their latest air defense systems, and so would be far better placed to develop weapons best suited to counter those radars and missiles. It is also not clear how much work the Russians put into making sure each exported system is distinct enough from others to not be easily compromised.
There would be no doubt that they would have taken steps to make sure the systems they export and those used by there own forces would be different enough that the West would not be able to get much useable information from access to exported systems to be able to compromise Russian defenses, but whether they go as far for all export customers is a different questions, and I have my doubts about how distinct each exported system is to others.
- Proximity and history between Israel and Syria. Israel is pretty much certain to have agents working in Syria. No matter how good a weapon system is, it will still be made useless if someone give the passwords to the enemy. May not be what happened, but it is certainly a possibility.
While all these factors would also apply to Russian missiles sold to China, Chinese air defense relies mainly on indigenous systems that outsiders would not have had any chance to study in detail. The Chinese also posses the technology to adapt and modify their Russian made missiles (they have been doing that since the Vietnam war to good effect), so even that potential weakness probably does not exist any more.
Just because the Israelis were able to such down the export version of Russian systems supplied to Syria is not any indication that they can do the same to China's.
It would also be interesting to know how the Syrian systems were networked. The Chinese have long relied upon hardline fiber-optic communications for their air defense network. It would be almost standard that such a network would be secure and isolated. That means you will need to physically access the hard line in order to gain access.
That is something we can pretty much rule out unless people start taking Clancy's wet dreams as reality.
