I'm not sure a service ( or even a govt) can counter much in that regard unless it has the means and will to do so. They might be able to protect cyber infrastrucutre which sort of seems more defense oriented, while leaving the cyber-mercenaries to continue offensive actions. Hard to respond to that without maybe crossing some political boundaries.

It may not be killing someone, but collection of information that is analyzed and turned into Intel as a service and then rapidly sent in digits to the person paying for those services can certainly make a difference in how bullets and bombs are employed effectively.
There's an unofficial sense among some AI researchers I know that the 8th Air Force is developing an electronic "scortched earth" cyber weapon that will flow through a distributed network, burning out each node. Of course, no one will admit it exists.