BOULDER - LogRhythm Inc., a Boulder-based software company that develops cyber-defense software, announced Thursday it has raised a $15 million Series D round.

Siemens' Venture Capital Group, the corporate venture-capital division of Siemens AG, led the round. Existing investors Adams Street Partners and Grotech Ventures also participated.

LogRhythm is developing technology in the security-information and event-management market. LogRhythm's platform manages and monitors network activity so security experts know when hackers attempt to access a network, giving system administrators information about potential attacks, among other capabilities.

LogRhythm's clients include financial institutions, health-care companies and government agencies. LogRhythm raised a $10 million Series C round in March 2011.

LogRhythm will use the money to accelerate growth, product development and international expansion, according to a press release from the company.

"We are excited to partner with Siemens' Venture Capital group, particularly due to the opportunity we see to collaborate in several of the key vertical markets that LogRhythm and Siemens both target, including health care and critical infrastructure," LogRhythm president and chief executive Andy Grolnick said in the release. "Network attacks and breaches are increasingly driving organizations to employ more advanced detection and response capabilities. There is also a rapidly growing demand for solutions that help organizations tap 'Big Data' for enhanced security, operations and business intelligence. LogRhythm's SIEM 2.0 platform addresses both of these burgeoning needs in unique and compelling ways."