U.S. equities took a beating on Monday, with declining issues outnumbering advancing issues nearly four to one on the New York Stock Exchange. The S&P 500 and the Dow Jones Industrial Average dropped 1.4% apiece, while the tech-heavy Nasdaq Composite lost 1.8% as technology shares underperformed.

Facebook (FB 172.56, -12.53) was the center of attention following weekend reports that research firm Cambridge Analytica gained inappropriate access to data on 50 million Facebook users. The alleged incident sent Facebook shares lower by 6.8% and was met with cries for greater regulation on data collection--which, in turn, weighed on fellow data collectors like Alphabet (GOOG 1099.82, -35.91, -3.2%), Twitter (TWTR 34.98, -0.60, -1.7%), and Snap (SNAP 16.42, -0.59, -3.5%).

Unsurprisingly, the technology sector--which is the most influential of the 11 S&P sectors, representing around a quarter of the broader market--finished at the bottom of the sector standings with a loss of 2.1%. The energy (-1.7%) and health care (-1.7%) sectors were the next-worst performers, while the financials (-0.9%) and industrials (-0.8%) groups showed relative strength, finishing at the top of the day's leaderboard.

The major averages were lower at the start of Monday's session, with the S&P 500 immediately dropping below its 50-day simple moving average (2748). Selling steadily drove the market lower into the afternoon, but a late bout of buying helped make things look somewhat better by the close. At its best mark of the day, the S&P 500 was down 0.4% and, at its worst, held a loss of 2.1%. The Nasdaq was down 2.6% at its session low, while the Dow never lost more than 2.0%.

U.S. Treasuries didn't receive much buying interest despite the equity sell off, with the benchmark 10-yr yield finishing unchanged at 2.84%. However, the defensive disposition was evident in the CBOE Volatility Index (VIX 19.43, +0.62), which spiked 25%, hitting a two-week high.

With no economic data due until midweek, investors turned their attention to the Fed's rate decision, which will be released on Wednesday afternoon. The market is all but certain that the central bank will raise rates, but the Fed's policy directive will still be highly influential as it will contain updated economic and rate hike projections.

• Nasdaq Composite: +6.4% YTD
• S&P 500: +1.5% YTD
• Dow Jones Industrial Average: -0.4% YTD
• Russell 2000: +2.3% YTD

Headlines provided by Briefing.com