London — Russian hackers hijacked  an Iranian cyber unit to attack governments and industrial organisations in dozens of countries while masquerading as attackers from the Islamic Republic, British and US officials said on Monday.

The Russian group, known as “Turla” and accused by Estonian and Czech authorities of operating on behalf of Russia’s FSB security service, has used Iranian tools and computer infrastructure to  hack in to organisations in at least 20 different countries over the past 18 months, British security officials said...