The phrase "shadowy group" refers to an organization or gathering of people that operates secretly or discreetly, often hiding their identities or activities from the public. Full definition
Spanish law officers are reporting that they have taken into custody three leaders of the vast, shadowy group of computer hacking ne'er - do - wells collectively known as Anonymous. (thatvideogameblog.com)
He delivered a video warning about it in his most recent Weekly Address, describing a «flood of attack ads run by shadowy groups with harmless sounding names.» (slaw.ca)
In 2013, independent expenditures by shadowy groups became a dominant talking point around the city's elections that year. (gothamgazette.com)