Short sellers are getting back into the stock market in hopes of a coming price correction.
Short interest—as measured by the average percent of shares out on loan in the S&P 500 index to hedge funds and others—is up more than 8 percent in the last eight weeks, according to financial information provider Markit.
"While most of the market's recent price appreciation was seen over the last month, we've also seen shorts add to their positions in line with the market swell," Simon Colvin, a Markit analyst, wrote in a report Tuesday.
"Shorts have already had a shot at the market after the slow start to the year. But the recent surge in demand to borrow comes on the heels of a price surge, something which has not been seen in the last 18 months of the rally," Colvin added. "Conversely, last year's strong rally in the first six months saw shorts steadily close out their positions."
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While shorting interest has increased, it's still low overall at less than 2.3 percent of all shares outstanding, Markit said.
The largest jump in short interest was in media companies. According to Markit, 12 of the 14 sector stocks in the S&P 500 attracted more bets against them, an average jump of 50 percent to an above-index average of 2.4 percent of shares outstanding.
Cablevision, the most-shorted media stock, saw demand to borrow jump by more than two-thirds to 12 percent over the last eight weeks. Other large increases were seen the shares of Gannett and CBS Corp.
Colvin notes that traditional short sector favorites such as consumer durables (companies that produce electronics, kitchenware and other long-term household purchases) and semiconductor makers have actually seen decreased interest in betting against them.
—By CNBC's Lawrence Delevingne