If small groups of individual "hackers" are capable of executing high-profile operations, just imagine the capabilities of nation-state cyberwarfare forces. The intelligence agencies of large governments employ thousands of professionals, all at least as qualified as the hackers behind these attacks. The difference is that government employees (or contractors!!) have no fear of legal repercussion restraining their operational activities.
When attacks like this move the market, any scrutiny of the attack must include analysis of market trading in the days following. Who profits from the drop in Anthem stock price? I imagine the SEC investigates this as part of due course, but one should consider that nation states are active investors in the stock market, whether directly or through hedge fund proxies. If a nation state can hack a large enterprise, and a nation state can trade large volumes of securities against that enterprise, then it follows that nation states can profit from cyber warfare.
The next five years are going to be very interesting.