Long rumored as an acquisition candidate, Fortinet found itself at the center of M&A speculation again on Thursday. The buzz was making the rounds, with the unified threat management (UTM) vendor paired with the increasingly acquisitive Dell. Fortinet shares currently trade about twice the level they came public at back in November 2009, with a market cap of $4.1bn.

Even a standard one-third premium on Fortinet’s current trading value would put the price in the neighborhood of $5.5bn. That would make this (still rumored) transaction the second-largest deal in the information security market, trailing only Intel’s $7.68bn purchase of McAfee. (McAfee garnered a roughly 60% premium.) Fortinet recorded sales of $433m in 2011 and will likely generate about $520m in revenue this year, so the company would almost certainly pull in a double-digit multiple.

Fortinet was founded by Ken Xie – who, along with his brother, still owns a significant chunk of the business – who already has a multibillion-dollar security exit. He sold his company NetScreen Technologies to Juniper Networks for $4bn in equity back in 2004. In the past, Fortinet has attracted attention from Dell, Cisco Systems and IBM, among other tech giants.

A pairing with Dell would make a great deal of sense. Foremost, Dell has a tremendous product distribution channel that could push along Fortinet’s appliances. More broadly, it would also fit well with Dell’s previous significant security acquisition, SecureWorks. Fortinet would boost the SecureWorks’ portfolio and make for easy management of those offerings.

This post was primarily written by 451 Research’s M&A Research Director Brenon Daly with input from Andrew Hay. For more M&A speculation, confirmation and postulation please follow 451 Research’s Inorganic Growth blog.