I hope you're not talking about the CIA, whose network of agents in China (to pick one example) was rounded up and killed due to either shoddy IT work or a mole in the Agency. Either possiblity reflects poorly on the American intelligence community:

https://www.reuters.com/article/us-usa-china-espionage-idUSK...

>Investigators remain divided over whether there was a spy within the Central Intelligence Agency who betrayed the sources or whether the Chinese hacked the CIA’s covert communications system, the newspaper reported, citing current and former U.S. officials.

>The Chinese killed at least a dozen people providing information to the CIA from 2010 through 2012, dismantling a network that was years in the making, the newspaper reported.

>One was shot and killed in front of a government building in China, three officials told the Times, saying that was designed as a message to others about working with Washington.

Intelligence I'd say probably Russia right? They've made America look quite incompetent the past decade or so. Military I'd say America although I don't think SEAL team 6 is going to be hunting down these attackers

Why are you bringing Israel into this?

The effectiveness of the CIA (or government) depends on the narrative of the author. Like the immigrant paradox: are they lazy or are they taking your jobs? which is it?

In terms of actual execution, definitely not America!

Pound for pound I'd say Israel.

In absolute terms I'm pretty sure China has us at sea and in cyber so...

Not the US

We should use it and shut down Russian pipelines. The Russian government is supporting and harboring DarkSide. It's possible the state directed this attack through them for plausible deniability.