Network equipment giant Cisco Systems on Thursday said it plans to acquire three-year-old security startup Securent for $100 million in cash and assumed options.

Venture capital firms Greylock Partners and Onset Ventures pumped $6 million into Securent, which was formed in 2004.

The purchase of Mountain View, California-based Securent will be Cisco’s twelfth acquisition this year and its second of a security firm. In January, Cisco announced its intention to acquire IronPort, a messaging security specialist for $830 million.

There has been a spate of security startup acquisitions by systems companies dating back more than two years, with Cisco, IBM, and EMC leading the spending spree.

A combination of new security regulations, Web 2.0, and user demand for anywhere-anytime access to corporate data is driving demand for stronger but more flexible security, and that is thinning the herd of security startups through acquisition.

“This all requires a whole new level of security thinking, and this pushes us to find vendors that can help solve some of these unique problems,” said Joe Burton, CTO of Unified Communications for San Jose-based Cisco.

The acquisition of Securent shows that the wave of consolidation in the security market is not over, according to In-Stat analyst Victoria Fodale, as the remaining startups jostle for position.

“VCs have lately been very picky about security startups in part because they rarely go public and are usually acquired by larger players, which tend not to do much R&D around security,” said Ms. Fodale.

Securent began marketing its software, which offers IT managers a single point from which to manage secure access to corporate data resources, in 2005.

“Cisco doing another security acquisition this year caught me by surprise, so it shows that the security consolidation phase is not over,” Ms Fodale said.