For nearly two decades, one of the world's most infamous hacker groups has operated under the name "Anonymous." And the mysterious online community is making headlines once again.

After Russia invaded Ukraine at the end of February, a Twitter account with 7.9 million followers named "Anonymous" declared a "cyber war" against Russia and its president, Vladimir Putin. Since then, the group has claimed responsibility for various cyberattacks that disabled websites and leaked data from Russian government agencies, as well as state-run news outlets and corporations.