Before starting an attack, the group is known to conduct reconnaissance of the people it is targeting, including identifying contacts from their social networks or “sphere of influence,” Microsoft said. Using names collected from that research, the group then creates fake LinkedIn profiles, email addresses and social media accounts to trick their targets into engaging in a correspondence. At a certain point, they include an infected file in the communications to get access to the target’s data.

The hacks fit a pattern of Russian behavior stretching back more than a decade. Russia-aligned groups have been accused of infiltrating government agencies, multinational corporations and other organizations across the United States and Europe. Mixed with online disinformation campaigns, the incursions have tried to influence elections, conduct espionage and sow social discord among Western democracies.

Even as the United States and European allies have bolstered their cyberdefenses, the attacks disclosed on Thursday show how any protections can be undercut by a simple mistake by an individual who clicks or downloads malicious files.

Russia has denied past accusations of hacking.

David Cameron, Britain’s recently appointed foreign secretary who previously served as the country’s prime minister, said in a statement that the attempts by Russia “to interfere in U.K. politics are completely unacceptable and seek to threaten our democratic processes.”

“Despite their repeated efforts, they have failed,” he said. “In sanctioning those responsible and summoning the Russian ambassador today, we are exposing their malign attempts at influence and shining a light on yet another example of how Russia chooses to operate on the global stage.”