Where did the company get its name? Proofpoint is intended to communicate the company's focus on statistical analysis techniques, as with a mathematical "proof," while "point" references the fact that the solution provides a single "point" of administration, analysis and policy application.

Who's using the product? Proofpoint claims more than 1,300 customers worldwide, including Bank of America, DeKalb Medical Center, Hertz, Hitachi Data Systems, Kaiser-Permanente, Mary Kay, NTT Communications, Outback Steakhouse, Pitney Bowes and T-Mobile.

3. Reconnex

Founded: October, 2003

Location: Mountain View, California.

CEO and background: John Peters was previously the CEO of several venture capital-backed companies, including Yipes, Netli, and Sigma Concentric.

Funding: US$37 million from NorWest Ventures, August Capital, Levensolhn Partners and Outlook Ventures.

What does the company offer? DLP appliances that combine network data monitoring and data-at-rest discovery features into one platform, while also providing features for controlling portable media and storage ports.

Why is it worth watching? Most DLP solutions do a good job of protecting fixed-format data such as Social Security and credit card numbers. Guarding unstructured data, on the other hand, is a more difficult proposition. Much intellectual property, such as source code, has no fixed format and requires more sophisticated search techniques.

Reconnex relies on indexed searches, which "enable organizations to automatically mine data and define group associations." Indexed searches allow organizations to find sensitive data via keywords, communication parameters, content types or other customer-defined concepts.

Where did the company get its name? Reconnex is a combination of the words "reconnaissance" and "exposure," highlighting the importance of having network visibility in order to control the flow of sensitive data.

Who's using it? The company claims more than 45 Fortune 1000 customers, including WebEx, Sirva, Medstar Health, BCD Travel and George Washington University.

4. Vericept

Founded: 1999

Location: Waltham, Massachusetts, and Denver

CEO and background: Dave Parkinson was most recently with Sigma Partners, where he was executive-in-residence. Prior to that, he was president and CEO of Books24X7, an e-learning company, and he was director, partner and CFO of Boston Consulting Group.

Funding: US$52 million from Sequel Partners, Sigma Partners, William Blair Capital Partners, Visa International and Globespan Capital Partners.

What does the company offer? DLP solutions that discover and analyze stored data, while also analyzing all Internet-based communication and attachments, including e-mail, instant messaging, peer-to-peer file sharing, chat rooms, blogs, Web postings, FTP and Telnet.