What does persistent engagement look like? Ask the Internet Research Agency.
US Cyber Command, supported by intelligence from the National Security Agency, shut off the internet for Russia's Internet Research Agency (IRA) on the day of the US midterm elections and for about a day afterwards, according to the Washington Post. Speaking anonymously, US officials told the Post that the operation was meant to prevent the troll farm from spreading disinformation during the vote or raising skepticism about the results.
After briefings held earlier this month, Senators of both parties credited Cyber Command with preventing foreign influence on the election, and regretted they couldn't share details with the public (Washington Post). The New York Times had reported that Cyber Command was sending direct messages to employees of the IRA and other Russian operators to let them know they were being watched, and Russian officials may have responded with a mole hunt (Naked Security). Rob Joyce, a senior cybersecurity adviser at the NSA, said on Thursday that the time has come "to alter the field and not just stand back and wait for [our] opponents to probe us" and that “we have to impose costs in a visible way to start deterrence.” He added that preparation to defend the 2020 election is already underway (CyberScoop).
The overall reaction to the campaign in the US has been positive. While some said operations like this aren't even close to a long-term deterrent, that wasn't the point. Defense officials told the Post that "grand strategic deterrence" wasn't the objective. Ben Buchanan (Lawfare) agrees, saying it was instead "an attempt to deny, temporarily removing an arrow from the Russian’s quiver." Jason Healey at the Cipher Brief says sometimes "you just have to stop adversaries from punching you." Cyber Command calls the strategy "persistent engagement."