Great interview with Imperva CEO Shlomo Kramer in Forbes.  The most interesting passage: 

Companies tend to react to cyber attacks rather than prepare for them, and malicious hackers meanwhile learn new tricks to circumvent the gates. “There is a dislocation,” says Shlomo Kramer, the chief executive of IT security firm Imperva and a 25-year veteran of the security industry. “The anti-virus market is not very useful against the new types of malware that come everyday. It’s a $10 billion market. It’s a renewal market.”

By “renewal,” Kramer means that IT managers at large companies — typically chief information officers (CIOs) — prefer to sign checks for the same, established software to protect their web applications, rather than make the uncomfortable changes necessary. It’s easier to do the former than change how money is spent, which can require all manner of approvals.

“But in security, the bad guys change and evolve,” says Kramer.