Earlier this year, Linux Web servers were getting hacked more often than systems running Microsoft Windows, but now Windows once again tops the list of most targeted online operating systems, according to Mi2g, a security intelligence company in London.Widely publicized vulnerabilities in popular applications for Linux led to a spike in defacement of websites hosted on servers running Linux in April and May. However, in June and July more websites hosted on Windows systems were successfully attacked. "The lesson we can learn is that it is difficult to say that one operating system is more vulnerable than another. It depends very much on the system administrator, the server software and third-party applications," says DK Matai, CEO of Mi2g.Just because Windows-based sites now get hacked into more does not mean that the open-source Linux system is more secure."People in the open-source movement have this mythical notion that they are more secure, that there is some kind of security through obscurity. But that is no longer true as more and more systems run open-source software," he says. Incidents of DefacementBriefing_graph.jpgForrester Research analyst Laura Koetzle believes Mi2g's figures mask a more serious problem. "What matters is not that one was compromised more in a particular month but when the vulnerabilities were discovered and how long it took for the vulnerabilities to be patched," she says. "Microsoft's job is to make it easier to patch systems."