Private equity firm Thoma Bravo plans today to buy UK-based cyber-security giant Sophos for $7.40 per share, for a total value of $3.9 billion, both companies announced today.

The sale price represents a 37% premium on the Sophos market trading price, as recorded on Friday, at the end of the trading.

The Sophos board of directors said they plan to "unanimously recommend" the acquisition offer to their shareholders.

Before today's announcement, Thoma Bravo acquired a minority stake in McAfee last year and was rumored to be interested in buying the whole company.

It is unclear how today's Sophos acquisition will impact plans to buy McAfee, but the two companies -- Sophos and McAfee -- are classic rivals on the cyber-security market and share a product portfolio, so the door seems to have closed on the McAfee deal.

Thoma Bravo was founded in 2003 and has quickly risen to become a major player on the capital market with more than 230 deals, mostly based around software, IT infrastructure, and cyber-security.

The equity firm has been one of the most active players on the cyber-security market.

Before that, Thoma Bravo also acquired storage, backup, and security appliance vendor Barracuda Networks for $1.6 billion in November 2017; software testing firm Veracode for $950 million in January 2019; DDoS mitigation firm Imperva for $2.1 billion in January 2019; and software firm ConnectWise for $1.5 billion in February 2019.

Thoma Bravo also previously held stakes in other cyber-security firms such as Tripwire, Blue Coat, Sonicwall, Digicert, and Entrust.

For its part, Sophos has also made a splash on the market, with acquisitions such as Dialogs, SurfRight (the company behind security software HitmanPro), Avid Secure, and, most notably, Invincea.