"That strike, often referred to as the Stuxnet attack, may have inspired the Iranians to begin a cycle of retaliation, a recently disclosed memo from Edward J. Snowden’s trove of National Security Agency documents indicates. Norse says it saw evidence that Iranian hackers probed the network of Telvent, a company now owned by Schneider Electric that designs software to allow energy companies and power grid operators to control their valves and switches from afar."