Microsoft's US general manager/chief security advisor for its National Security Team thinks like a true security professional: In every bit of good news, Bret Arsenault wonders what bad news could be lurking behind it.

Speaking at the Boston SecureWorld conference Wednesday, the 19-year Microsoft veteran whose job includes protecting enterprises, developers and Microsoft itself said there actually is plenty of good news on the security front. For example, his outfit scans a half million devices (with customer permission) per month and in the first half of last year saw the first period-over-period decline in new vulnerabilities disclosed across Microsoft and non-Microsoft software since 2003.

However, 3,400 new vulnerabilities were discovered and "it's still a big number," Arsenault says. "So if vulnerability rates are down, where are they?"

One trend that pops out is that attackers are increasingly laying off operating systems and exploiting applications instead. One reason for this, Arsenault says, is that vendors like Microsoft, Apple and Red Hat have done a good job in recent years securing the IP stack and operating system.

Arsenault pointed out that the first operating system hardening guide Microsoft wrote for Windows 2000 came 18 months after shipment of the product; the next (for XP Service Pack 2) was within 90 days of product shipment. With Vista and other new products, Microsoft ships the hardening guide along with the product. "On the application side, on the other hand, we're very far behind," Arsenault said (though he said the Office 2007 hardening guide is very solid, even if it did take a year-plus to release it).

"You have your classic arms escalation race between the hackers and the people who are trying to protect [software], so [the hackers] go after the easiest target that's least protected," Arsenault said. "The application space is the next space in the model they're going after," and he sees this continuing to be the case for at least the next few years. And Arsenault is talking about Office as well as CRM, ERP and other programs that contain the sorts of data that financially motivated hackers crave.

"This is not a problem that people should be thinking is just an Office problem," he said. "It's anybody who uses file formats that are not XML based going forward." Adobe, Corel and Google are among others facing similar challenges, Arsenault said.

Microsoft has made fixes to older products, such as Office 2003, but Arsenault emphasizes that it's a lot harder to retrofit an old product for a new environment than it is to build a newer product, say Office 2007, more securely. He made an analogy about the tradeoffs of updating older software to his desire to add airbags to his 1992 Toyota: He can (and will) actually get it done, but it's going to cost him.