Trusted Network Technologies (TNT), the developer of the Identity firewall for internal networks, has raised a $12 million second round of financing ahead of schedule.

New investor JK&B Capital led the Series B round and was joined by existing investors, Charles River Ventures and Flagship Ventures, bringing the total venture capital investment in Atlanta-based TNT to $18 million.

The additional capital will be used to accelerate development of the Identity product platform, as well as expand the company’s marketing and sales effort, it says.

“We weren’t looking for investors, but TNT was approached by JK&B, a leading VC with expertise in the security space, with an offer we couldn’t refuse,” said Steve Gant, president and CEO of TNT. “With these resources, we are prepared to launch into the next innovative stage of product development to broaden the applications for our core technology and fulfill our technical vision.”

Tasha Seitz, a JK&B partner, will become a TNT director, and Marc Sokol, also a JK&B partner, will be joining TNT’s technical advisory board.

“TNT has developed technology that bridges a major gap between identity management technologies and perimeter security solutions which are identity-blind,” Seitz said. “Identity ensures the privacy, integrity and confidentiality of an organization’s critical data. There’s no one else out there doing what TNT is doing.”

Last week, TNT released version 1.6 of Identity. The identity-based firewall enforces access control policies at the network level. It identifies users on the network…at the packet level…so that only authorized users, wired or wireless, can connect to protected assets, while unauthorized users cannot.

The next stage of product development, TNT says, will incorporate “health check” technology, which will ensure that authorized users have the appropriate anti-virus, personal firewall or OS patch level, and reject or quarantine that user before connection if they are not up to date.

“Identity is helping customers protect their networks and attain regulatory compliance at a fraction of the cost and complexity of traditional security approaches,” said Jim Matheson of Flagship Ventures. “Identity customers come from industries dealing with significant regulations regarding the safeguarding of data–. Our continuing commitment reflects our enthusiasm for this market opportunity and for TNT’s ability to take their revolutionary technology in an exciting direction.”