SAN FRANCISCO — For more than a year, a group of cybercriminals has been pilfering email correspondence from more than 100 organizations — most of them publicly traded health care or pharmaceutical companies — apparently in pursuit of information significant enough to affect global financial markets.

The group’s activities, detailed in a report released Monday morning by FireEye, a Silicon Valley security company, shed light on a new breed of criminals intent on using their hacking skills to gain a market edge in the pharmaceutical industry, where news of clinical trials, regulatory decisions or safety or legal issues can significantly affect a company’s stock price.

Starting in mid-2013, FireEye began responding to the group’s intrusions at publicly traded companies — two-thirds of them, it said, in the health care and pharmaceutical sector — as well as advisory firms, such as investment banking offices or companies that provide legal or compliance services.

The attackers, whom FireEye named “Fin4” because they are one of several groups that hack for financial gain, appear to be native English speakers, based in North America or Western Europe, who are well versed in the Wall Street vernacular. Their email lures are precisely tailored toward each victim, written in flawless English and carefully worded to sound as if they were sent by someone with an extensive background in investment banking and with knowledge of the terms those in the industry employ.