Pavlo Gonchar | Lightrocket | Getty ImagesCybersecurity firm Proofpoint announced Thursday it will acquire European rival Hornetsecurity for $1 billion to strengthen its European presence as it explores a return to public markets.The deal marks the single largest acquisition in Proofpoint's history.The cybersecurity industry has seen heightened consolidation in recent months, with companies snapping up smaller competitors to bolster their offerings in an era of AI-fueled cybercrime.In March, Goo...