Updated from 11:27 a.m. EDT
NEW YORK (TheStreet) -- Shares of St. Jude Medical (STJ) were declining 5.81% to $77.12 on heavy trading volume early Thursday afternoon after Carson Block's research firm Muddy Waters said that it is short the stock.
Muddy Waters believes that the Saint Paul, MN-based medical device company is set to lose more than half of its revenue for a period of at least two years due to device recalls, Block told Bloomberg.
He explained that St. Jude's Merlin@home data transmitters lack a secure communication protocol, representing "relatively low-hanging fruit for attackers to exploit."
For a number of years now, St. Jude has been putting profits before patients, Block said in the Bloomberg interview.
St. Jude has since issued a statement claiming the allegations are "absolutely untrue," CNBC reports.
About 12.88 million shares of St. Jude have been traded so far today, well above the stock's average trading volume of roughly 1.85 million shares per day.
Separately, TheStreet Ratings team rates the stock as a "buy" with a ratings score of A-.
St. Jude Medical's strengths such as its revenue growth, good cash flow from operations, solid stock price performance, expanding profit margins and notable return on equit outweigh the fact that the company has had sub par growth in net income.
You can view the full analysis from the report here: STJ
TheStreet Ratings objectively rated this stock according to its "risk-adjusted" total return prospect over a 12-month investment horizon. Not based on the news in any given day, the rating may differ from Jim Cramer's view or that of this article's author.