FILE PHOTO: The AT&T logo is seen on a monitor on the floor of the New York Stock Exchange (NYSE) in New York City, U.S. June 13, 2018. REUTERS/Brendan McDermid
The companies did not disclose the value of the deal, which they said they expect to close in the third quarter.
AT&T is buying AlienVault as large telecommunications and technology companies including Cisco Systems Inc, International Business Machines Corp and Verizon Communications Inc expand sales of cybersecurity products, among the fastest growing segments of the technology industry.
San Mateo-based AlienVault raised $52 million in 2015, bringing total funding to about $116 million, according to a press release on its website. Investors included Intel Capital, Kleiner Perkins Caufield & Byers and Trident Capital.
Reporting by Angela Moon; Editing by Jim Finkle and Frances Kerry