SecureData has been acquired by French comms goliath Orange for an undisclosed fee.
The Maidstone-based security provider hit sales of £35.4m in the year ending 31 July 2017 and claims to be the UK's largest independent cybersecurity provider.
Ian Brown, executive chairman at SecureData, said: "We are both thrilled and excited to be joining the Orange Cyberdefence family.
"Both organisations share the same vision and aspiration for the cybersecurity market, and have many complementary services and skills.
"By being part of Orange we will be able to better serve the international needs of many of our existing customers, as well as providing enhanced cyberservices to Orange customers in the UK."
Orange said that SecureData will work alongside its existing security operations in France and Belgium.
The French firm said that the addition will bolster its European credentials.
Executive director Hugues Foulon said: "We are very proud and happy to announce the acquisition of SecureData, which will mark a major milestone in Orange's development in Europe's cybersecurity market.
"SecureData, just like Orange Cyberdefence, has successfully made the transition towards managed security services, and shares the same passion for cyber.
"Cybersecurity has become a critical element for both large and small companies as they evolve in an increasingly digital-reliant world. We are convinced that the combined expertise of Orange Cyberdefence and SecureData will provide a powerful resource for our customers in ensuring the protection of their valuable data."
Telecoms giant Orange hit sales of of €41bn (£36bn) in 2017 and has 150,000 employees worldwide.
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