Despite the turbulence of the market this week, it held its own and, despite some initial ups and downs, remains a few bucks ahead of its opening price.

The company has joined a very exclusive club of open source companies that have gone public: Red Hat, VA Linux, TurboLinux, Mandriva, Trolltech and when it was still open source, Caldera, now the open source-loathed SCO. MySQL has IPO designs and could be next.

Sourcefire backers, which funded it to the tune of $54 million, include New Enterprise Associates, Sierra Ventures, Sequoia Capital, Inflection Point Ventures and Core Capital. Morgan Stanley and Lehman Brothers handled the IPO.

The six-year-old company lost $865,000 on revenues $44.9 million last year although the second half was profitable to the tune of $2.2 million. There is however a trade secrets suit hanging over its head, which, if nothing else, add to its expenses.

Its users include the 30 US agencies.