Apple sought to reassure customers today that the fix--created for a security flaw that would allow a third party to corral some Apple computers in a "denial of service" attack--indeed works properly, and that at least some of the reported problems could be a case of simple misunderstanding.

Yesterday, customers learned of the potential flaw in Apple networking software that could potentially allow a malicious programmer to use Macs to attack other computers under a limited set of circumstances.

Users posting comments to various Web sites such as Apple's own online support site noted a variety of maladies after installing the software, including network connections that were unstable or impossible to maintain and problems running other software such as Internet browsers.

In some instances, the problems can be cured by not using the software. The patch is only needed by Mac users if their computer is hooked up to the Net via "always on" digital subscriber line (DSL) or cable modem connections, said Phil Schiller, vice president of worldwide marketing for Apple. Users with dial-up modems don't need the software, he said.

Barring that exception, some other problems might be cured by a push of a button.

Network settings often change after each time a computer initiates a connection to the Net, because many service providers assign a computer a new IP (Internet protocol) address each time--a practice analagous to giving out a new phone number or home address to uniquely identify a user every time someone makes a call.

Normally, if a user's network settings are changed, they take effect immediately, Schiller explained. He said that the software patch works correctly, but in this instance the computer needs to be restarted if settings are changed. Future versions of the fix will rectify that issue, he said.

However, if a user's settings are always changing--in other words, the IP address is different every time the computer is turned on--the patch isn't needed, he said, because an attacker has to know the computer's address in order to exploit the vulnerability.

The fix was issued because Mac computers could be used to aid in what's known as a denial-of-service attack. According to the Carnegie Mellon University's Computer Emergency Response Team, in such a circumstance: "Intruders can flood networks with overwhelming amounts of traffic or cause machines to crash or otherwise become unstable."

Dr. John Copeland, who chairs the Georgia Institute of Technology's School of Electrical and Computer Engineering, recommended that the correction for the flaw be applied before New Year's Eve in order to prevent the Macs from being used to attack other computers. Copeland was first to uncover the issue.

As previously reported by CNET News.com, security experts have warned of a possible concerted effort to attack computers on New Year's Eve although no direct evidence of any plots has been gathered.