Both have massive ground based laser system designed to take out sats. In fact , ussr once threatened the shuttle by hitting it with a laser on the window. Purposely. Now, Russia AND china, have small sats about size of basketball that they are moving slowly by American sats. These are only useful as a first strike weapon. Basically, if we launch at attack, upon launching, we do not need the sats. OTOH, if Russia, and/or china, launch, then taking out sats first, give them a critical edge.
Those are probably "inspector satellites". They listen as they pass by. Every computer chip or electronic circuit with AC components is a little antenna, emitting radio waves of frequencies in accord with, say, a CPU's clock speed.
One of your 'basketballs' wouldn't need to have anything but a set of antennas to receive the RF leakage. It would just collect... Once it was done listening to exactly what is going on inside the US satellite's circuitry, it could just give a short puff to speed it up a bit along its orbital path. In a month or three, it would catch up with the 'mother ship', perhaps an innocuous weather satellite on a similar path, but 1/2-way around the planet from the target of the espionage.
Once close enough to home, it could just use near-field radio communications to dump its data to mommy — conceptually like WiFi or Bluetooth – omnidirectional so signal is only strong locally. Frequency-hop, do it in bursts, etc. The mother ship, big and always talking to the ground, could just weave the data into its usual stream down to earth. Once on earth, computer analysis could commence.
What could be learned? Oh, lots! The interest, at least on the first runs, would not be on what the satellite was doing at the time. Rather, the goal would be to determine the specs. of that bird's capabilities &/or functions. Specifications, as in how good is it at looking and listening? That's Top Secret and/or Program-specific Classified info – the kind that requires you to have serious clearances before you can go sit in a vault (a SCIF) and read the details. You can't take any notes with you when you're done, so you'd better enjoy memorization. . . or a nap.
So really, although your basketballs could be conventional shrapnel bombs, it is far more likely that they are Inspector Satellites, spying on adversaries' spy/comm satellites to learn their capabilities, specs, and possibly function. The US-SMC and NRO are crazy-protective of such information, as you might imagine.
I heard the above from SWIM.