NEW YORK/BOSTON (Reuters) – Rapid7, LogRhythm and Mimecast are joining a growing list of cybersecurity firms planning to go public in 2015 to capitalize on investor interest following a spate of hacker attacks, according to people familiar with the matter. Shares of publicly traded cybersecurity firms have outperformed the market in recent months, as high-profile data breaches at Sony Corp, JPMorgan Chase & Co and Anthem Inc prompt businesses to spend more to secure their computer networks.