By Lynn Cowan Of DOW JONES NEWSWIRES Security-software company Proofpoint Inc. (PFPT) saw its shares jump sharply on their opening trade Friday, the company's first day as a public stock. The stock opened at $16.85 a share on Nasdaq, up 30% from its initial public offering price of $13. A total of 6.3 million shares were sold in the offering--more than had been expected--at a price above the estimated range of $10 to $12 a share. Proofpoint specializes in security software for large and mid-sized companies, providing protection against data theft, regulatory compliance, archiving and secure communication. The company has said a shift in the sources of cyber crime from hackers toward organized crime and governments, combined with international data trafficking, is driving a large wave of attacks on data. At the same time, more businesses are collaborating online and their employees are using mobile devices and Internet applications that can reduce the effectiveness of existing security software. Proofpoint has said its software protects information as it flows to and from its users, and can securely archive it, too. Its software, sold on a subscription basis, is used by about 2,400 customers around the world, including 26 of the Fortune 100 companies. It markets its products through its own sales team and through distributors and resellers, as well as through strategic partners such as International Business Machines Corp. (IBM), Microsoft Corp. (MSFT) and VMware Inc. (VMW). In 2011, Proofpoint's revenue rose 26% to $82 million, while it reported a net loss of $20 million compared to a loss of $21 million in 2010. The company has never been profitable. Competitors include Symantec Corp. (SYMC), Intel Corp.'s (INTC) McAfee division, Cisco Systems Inc. (CSCO), EMC Corp. (EMC), Google Inc. (GOOG), and Hewlett Packard Cos. (HPQ). -By Lynn Cowan, Dow Jones Newswires; 202-257-2740; firstname.lastname@example.org --Mia Lamar contributed to this article.