Of the major indices, Facebook weighed most heavily on the tech-rich Nasdaq Composite Index, which was down 0.9 percent to 7,411.34 about 20 minutes into trading.
The Dow Jones Industrial Average dropped 0.8 percent to 24,749.76, while the broad-based S&P 500 dropped 0.7 percent to 2,733.09.
EU Justice Commissioner Vera Jourova called "horrifying" reports that Cambridge Analytica, the data analysis firm hired by Donald Trump's 2016 presidential campaign, stole information from 50 million Facebook user profiles to help design software to predict and influence voters' choices.
Facebook suspended Cambridge Analytica, but pushed back against the claim of a data breach, suggesting misused data was limited to a far smaller group of users.
Other large tech firms also stumbled, with Amazon losing 1.3 percent, Google-parent Alphabet 2.2 percent and Microsoft 1.4 percent. Apple shed 0.7 percent.
Tech shares were the worst-performing of the major sectors, but the broader market also has been pressured over the last couple of weeks by worries over a potential trade war and the prospect of more aggressive Fed rate hikes due to faster growth and inflation.
The Fed is expected to raise interest rates on Wednesday and will release its quarterly economic projections which will include officials views of the path of rates over the coming years.