For months, the Department of Homeland Security has known about Russia’s election interference but kept it secret, a whistleblower reveals, because the White House told them to. The department failed to provide homeland security; it abandoned its constitutional duties.

Some good news: Russia and China now oppose each other, respectively supporting and opposing Trump’s reelection, trolling for and against him in cyberspace. One hopes that this wedge will help drive our two main adversaries apart.

Russia has been continuously pro-Trump since early 2016. Facebook sold personal data to a data-mining operation in Britain, which sent the analyses to the Russian troll farm in St. Petersburg. An effective, low-cost way to harm their adversaries, as Russia has done in Europe by supporting anti-system parties with cash and cyber operations.

China appears to have been conflicted until recently. They liked how Trump weakens America and undermines trans-Pacific trade pacts, but they hated his unpredictability and tariffs on Chinese imports. Beijing seems to have settled on turning anti-Trump, although China does much less trolling than Russia.

Making matters more complicated, Iran, who hates Trump, is now switching sponsors from Russia to China. Iran, aside from Russian arms purchases, does a lot more commerce with China, especially in energy exports. Pipelines and seaports, part of China’s self-aggrandizing Belt and Road Initiative, will tie Iran to China. Putin surely doesn’t like that.

Another factor: Putin wants Iran/Hezbollah to leave Syria and not trigger a war with Israel in Syria. Putin wants Syria neatly wrapped up without competition, one aim of the recent highway ramming of a U.S. Army vehicle in northeast Syria. So, will Trump stand up to Putin over that or anything else? Doubtful.

Are Facebook, Twitter and the like now sufficiently vigilant to flag and/or delete “inauthentic posts” of any origin? They claim their cybersecurity teams sniff out trolls, but how thorough and timely are they? They make big advertising revenue from carrying troll-originated pages and have until recently feigned ignorance.

Let’s not give them a pass on this. Instead, let citizens and the print media catch fakes and embarrass the platforms into dropping them. It would be fun, too, and pique reader interest: How many trolls can we catch? Readers would submit suspicious pages, then experts could appraise their origin and intent. Such columns could be headlined “Troll Patrol” or “Don’t You Believe It!” Europe now educates citizens to detect disinformation; so should we.

Russian trollsters hide their origin. Their English may be good, but slips in grammar and word-choice have often given them away. Recently they have taken to encouraging unsuspecting Americans to write posts for “evenhandedness” and “peace” using frames supplied by unseen Russian editors. Just because a post looks American doesn’t mean it is.

Catching trolls is tricky, as they can take several sides. Their disinformation chiefly tries to sow doubt and chaos. Thus one trollster could support Black Lives Matter while another pushes Dixie Heritage and a third denigrates mail-in ballots. Anything to get Americans to distrust democracy and each other.

Russian trollsters admire and want to join the cool young Americans who develop apps and platforms in Silicon Valley. Accordingly, if employees of Russia’s Internet Research Agency, a front for their military intelligence, step forward and reveal its operations, reward them with H1-B visas and U.S. jobs. I bet we get some takers.

Mail-in ballots actually increase voting security because they have paper trails. But we must guard against cyberpenetration of voter registration. Just transposing two digits of the registration number, say, of every eleventh registered Democrat, would bar that person from voting. By the time the deliberate error is corrected, it would be too late.

The Trump administration, by denying Congress in-person intelligence briefings, attempts to conceal and minimize Russian penetration. Trump rightly fears that Russian help muddies his legitimacy, so he denies the charge as a hoax. Republicans, however, may be future victims.

Both Putin and Trump ignore the nerve-agent poisoning of Alexei Navalny, now in a Berlin hospital, the latest of many victims. Germany — tied to Russia by natural-gas pipelines, some undersea — debates the trustworthiness of a regime of assassins; so should we.

We should also remind Moscow that two can disinform. American trolls can deepen growing Russian discontent over economic stagnation, corruption and misrule that have cut Putin’s popularity in half. Protests flare in Belarus and Khabarovsk.

Retaliating too strongly, too soon shows Russia our capabilities and allows them to repair weak spots. We need to hint at our capabilities with an implied threat of escalating to kinetic (goes bang). For example, introducing errors into the guidance system of Putin’s proclaimed hypersonic missile (which may not be operational) could force Russia to test fire one. If they do, we gain valuable data. The message: Okay, Putin, how far do you want to take this?