Private equity firm Thoma Bravo agreed to buy Sophos Group Plc for $3.8 billion, taking the British cybersecurity firm private in the biggest takeover of a U.K. technology firm this year. Thoma Bravo will pay $7.40 a share in cash, or 583 pence per share, representing a premium of 37.1% to its last closing price, the buyout firm said in a statement Monday. Shares jumped as much as 38% in London on Monday and traded at 576 pence at 10:34 a.m.