Deal hoped to go through before year’s end after regulatory approval.
The defence company BAE Systems has agreed to buy cybersecurity firm SilverSky for £144.4m.
SilverSky, also called the Perimeter Internetworking Corporation, specialises in security-as-a-service, with its portfolio including managed services, email protection and network security.
Ian King, chief executive at BAE said: "The acquisition of SilverSky enhances our strategy to grow BAE Systems’ Applied Intelligence commercial cyber security business.
"SilverSky has an established sales force, a complementary suite of scalable products and a large installed customer base, providing a proven route to commercial markets in the US and other countries for our combined capabilities."
BAE will be funding the purchase through existing cash reserves, with the company hoping to close the deal before the end of the year pending regulatory approval.
SilverSky is headquartered in the Greater New York Area with a focus on the US market, and the firm expects to generate annual sales worth around $75m by the end of December through its customer base of 5,500, spanning several industries and firm sizes.
"This acquisition will further strengthen our ability to deliver the most comprehensive set of cloud-based security software and managed services," said Tim Harvey, chief executive of SilverSky. "Our customers will benefit from BAE Systems’ global presence and history of continued innovation."