F-Secure Corp. on Tuesday unveiled security software for open-source Samba file servers and Linux, addressing a need that's growing within the enterprise market.

The Finnish company announced the availability of antivirus software for Samba that automatically detects and removes viruses from files stored on the server. The new product is meant to protect all Samba-attached computers from malicious code that could enter the network from a Windows or Linux machine.

Next month, F-Secure plans to ship a Linux version of F-Secure Policy Manager, which will extend centrally managed virus-scanning to Linux workstations. The current product, which only runs on Windows, supports virus scanning on Windows-based workstations, Microsoft Exchange, and F-Secure's firewall, gateway, and other products.

F-Secure software supports products from Linux distributors SuSE (which was recently acquired by Novell), and Red Hat Inc. Both new products are sold on a per-CPU basis.

The vast majority of viruses and other malicious code traveling the Internet today target applications running on Windows-based PCs and servers. Analysts, however, say the number of viruses targeting Linux computers is Increasing, as more and more enterprises deploy business software on the open-source operating system.

In the fourth quarter of 2003, revenue from Linux servers increased 63.1 percent year-over-year, to $960 million, according to International Data Corp. Unit shipments for the quarter jumped 52.5 percent.

A Linux-targeted virus typically enters through a network interface and causes a buffer overflow in a running application. As a result, the infected application executes the invading virus.

These viruses are particularly dangerous because they are typically executed without warning.

"These viruses are automated and don't require any human interaction to launch," Laura DiDio, analyst for market researcher The Yankee Group, said. "That makes them stealthier and harder to detect."

Among the better known viruses that targeted open-source software were Flapper, in 2002, which attacked Apache Web servers; and Ramen, which hit systems running default installations of Red Hat Linux 6.2 and 7.0.

Focusing only on securing Windows computers, while ignoring Linux machines, leaves a serious security hole, since a virus can travel to any system once inside a network.

"People say Windows is still the main target, and that's true. But Linux is growing," DiDio said. "[Linux] is a small threat, but even a small threat can translate into a high risk."