SecureLink, owned by private equity investor Investcorp since 2015, has ops in eight European countries including the Nordics, Netherlands, UK and Germany.
It turned over €248m in sales in 2018.
The portfolio includes remote security software, along with specialised consulting, maintenance and support services including 24/7 security operation centres.
SecureLink has itself snapped up various security houses including ZIONSECURITY and reseller Nebulous.
Some 660 SecureLink faces will join Orange, a subsidiary of France Télécom, taking the total headcount of infosec personal at the telco to around 1,800.
The combined businesses would have had revenue of €600m in 2018, Orange claimed.