But the 2015 poisoning of Emilian Gebrev, an arms manufacturer in Bulgaria, helped expose the unit to Western intelligence agencies — and shed light on a campaign by the Kremlin to eliminate Moscow’s enemies abroad and to destabilize the West.

Related: Russia’s economy is sputtering, but the country has had tremendous success this year in disrupting a world order once dominated by the U.S. Our Moscow bureau chief, Andrew Higgins, examines how a country that former President Barack Obama once dismissed as a “regional power” has become such a potent force.

A rare win against online child sexual abuse

On a borderless internet exploding with imagery of child sexual abuse, anyone who campaigns to remove apps and websites with illicit material fights an uphill battle. That’s partly because tech companies in the U.S. and Europe have policies that can be exploited to shield criminal behavior.

One Canadian nonprofit used a computer program to force three sites offline last month. But the campaign took years, and its success is likely to remain rare.

Go deeper: Our reporter looked at the software that child protection hotlines are using to crawl the web for illegal imagery.