The omnipresence of software firms is triggering substantial antitrust concerns, calling into question the adequacy of existing regulatory frameworks. This study explores this pivotal concern in the context of the software industry, which is characterized by profound network externalities among customers and a rapid pace of innovation. Our study used the event study methodology on data from 252 antitrust cases involving the U.S. Federal Trade Commission and U.S. Department of Justice from 2000 to 2022, which revealed important insights into the differentiated effects of U.S. antitrust announcements on the market value of software firms. Although antitrust announcements generally have a negative impact on market value, software firms in this study displayed notable resilience compared with other sectors within information technology, such as hardware. Of interest is the negative relationship identified between R&D intensity and abnormal returns, which challenges traditional perspectives on the role of R&D in market competition and risk mitigation.