Sen. Mark Warner, D-Va., on Tuesday rolled out the first in a series of bills aimed at regulating Facebook and other social media companies, even as the path to an all-encompassing federal online privacy law remains murky.

The bill, which Warner introduced with co-sponsor Sen. Deb Fischer, R-Neb., bans online platforms with over 100 million monthly active users from using so-called "dark patterns." The term refers to interfaces designed to coax users into taking actions that often result in giving up more information than the user realizes — such as prompts to access phone and email contacts in order to keep using the platform.

The legislation, known as the Deceptive Experiences To Online Users Reduction (DETOUR) Act, would also create a regulator within the Federal Trade Commission that would enforce best practices as platforms evolve to protect users' interests.

The effort is one of several aiming to rein in social media companies in the wake of data breaches, privacy scandals, and harsh scrutiny of practices that allow harmful content to be disseminated. The focus on specific issues such as dark patterns comes in the absence of progress on broad-based regulation, despite seemingly bipartisan support building in the year since Facebook CEO Mark Zuckerberg testified on Capitol Hill.

So far, a few tech companies and industry groups — including Microsoft, Mozilla and Common Sense — have pledged to support it. Warner discussed the bill with Google CEO Sundar Pichai during his trip to Washington two weeks ago.

Roger McNamee, a longtime Silicon Valley venture capitalist and early Facebook investor, called the practice of employing dark patterns "low-hanging fruit" on Capitol Hill.