Check Point Software Technologies Wednesday launched a Windows Vista version of its flagship ZoneAlarm firewall and blamed the delay on a switch to the new operating system's application programming interfaces (API).

The Vista version of ZoneAlarm, a two-way firewall that will continue to be given away, is the first from a major security vendor to apply Vista's Windows Filtering Platform (WFP) API, said Laura Yecies, the general manager of Check Point's consumer security line.

"This is a bit later than we would have liked," said Yecies, noting the four-month lag between Vista's retail release and ZoneAlarm's appearance. "We underestimated the schedule impact of WFP. But long term, WFP will give us more support and more stability on Vista. It was a lot of extra work, but we'll have to do fewer hacks in the future."

WFP, a new Vista architecture that lets developers tap into the TCP/IP processing path, was a hard row to hoe. "At times, it seemed like we were an extension of Microsoft QA. They patched and made changes based on what we found while we were developing," Yecies said. Microsoft used WFP to create its own Windows Firewall, which is bundled with Vista.

Even so, Check Point is committed to keeping ZoneAlarm a free download.

"It's very important to who were are," Yecies said. Zone Labs, which was acquired by Check Point in 2004, made its name by giving away the firewall. "And we think it's the right thing to do," she said. "Our paid users live in a safer world because there are 20 million more protected by the free firewall."

Check Point touted ZoneAlarm, also the foundation of the ZoneAlarm Internet Suite that was released Wednesday for Vista, as an "operating system-level" firewall. "Eighteen months ago, we decided that the firewall had to operate at the lowest level of the OS, to monitor every call, every program," said Jordy Berson, ZoneAlarm product manager.

"There are so many new threats that we need a behavioral-based firewall" to detect and defeat more insidious attackers, including rootkits and drive by-installed keyloggers, Berson said. "ZoneAlarm does for the computer itself what it was already doing for the network," she said. The Vista firewall tracks 30 different behaviors, such as API calling, logging keystrokes or injecting code, then decides if what it's seeing is safe. If not, it shuts down the process as a more traditional firewall shuts down access to the Internet when it spots a rogue.

ZoneAlarm's delay had nothing to do with the brouhaha last year over access to the kernel in the 64-bit version of Vista, Yecies said. Last fall, several security vendors, including Check Point rivals Symantec and McAfee, pressed Microsoft to back off its PatchGuard kernel-protection technology. Eventually, Microsoft agreed. In December, the company released draft APIs.

"Interesting questions, but it was a separate issue," said Yecies, who then launched into criticism of PatchGuard and Microsoft's APIs. "They won't solve the problem [of hackers cracking the kernel]," she said. "If there is some new unknown threat in the future, the APIs won't help you. [Microsoft] would need to react, update and distribute the APIs to millions."

Yecies drew a line in the sand. "We're going to do whatever it takes to protect customers, even if it means hacking PatchGuard."

The free ZoneAlarm firewall will be available for download from the Check Point site later Wednesday. ZoneAlarm Internet Security Suite 7.1, priced at US$39.95 (a three-user pack is US$49.95) should also appear Wednesday. Customers with current subscriptions to earlier editions can update to the Vista version free of charge.