For the World of Warcraft, the ability to propagate the damaging and viral effect across the world was unintended. For Second Life, self-propagation is a feature that helps the world's users also become content creators.
"Attacks are, to some extent, a result of the decisions that we have made to allow a broad range of functionality in Second Life so that our residents are able to create as much interesting content as possible," Douglas Soo, studio director for Linden Lab, said in a recent email interview. "Unfortunately, much of the functionality that is used to make Second Life the fascinating place that it is can also be used to create disruptive attacks."
Second Life's residents can create pets that reproduce, flowers that spread, and objects that attach themselves to nearby avatars. Yet, those same abilities give a malicious creator all the tools needed to flood the world with bouncing balls or spinning rings.
While the graphical trappings might hide it, grey goo is nothing by a denial-of-service attack, consuming scarce resources such as server processor cycles and network bandwidth, said Soo.
"In the same way that it is theorised that out-of-control nanotech could consume all of the physical resources of the world and turn it into grey nanotech goo, Second Life grey goo can theoretically consume all of the available server resources of the Second Life world and fill it with grey goo objects," he said.
Balancing the features needed by in-world developers against the need to stop self-replicating attacks is a fine line for the company to walk. Linden Lab has approached the problem by improving its response tools, creating defenses against self-replicating attacks and making its system of servers more robust, Soo said.
To combat grey goo attacks, the company has implemented a ceiling on how fast objects can replicate and also limited the replication from crossing region boundaries in Second Life. Called a grey-goo fence, the defensive measure failed to stop the most recent attack because the rings propagated at a much slower rate, under the fence's throttling threshold.
"We don't want to completely eliminate the capability for self-replication because it can be used by legitimate designers and scripters to model artificial life, objects that grow and change over time, and many forms of 'art' projects," Joe Miller, vice president of product development stated on Tuesday in an email interview with SecurityFocus.
Rival virtual world, There.com, has taken a different tack.
Makena Technologies, the company that manages the online world, allows developers to create their own content, but must approve the digital objects before they are allowed to be injected into the game. By instituting an approval process, the company can prevent X-rated content from entering its PG-13 world, keep out object that may infringe on others' intellectual property and stop security threats from entering There, said company CEO Michael Wilson.
"The core attraction of There is that it is a great place to socialise and meet people," Wilson said. "Do people come to There to necessarily create their own content? Some do, but many would rather buy stuff and create a cool-looking avatar." (corrected)
Yet, for Second Lifer "Lioncourt," the freedom to make his own content without an approval process has led to a part-time income of hundreds of dollars a month.
"If (Linden Lab) has to remove the ability to (self-propagate), it is going to cut down the number of things in world," Lioncourt said. "If they put that restriction in place, it would cut down on the freedom people have in world."
To Lioncourt, such restrictions would make Second Life a less appealing place to visit.
CORRECTION: The original article dropped some words from Makena Technologies' CEO Michael Wilson's quote. The words have been re-added.
This article originally appeared in Security Focus.
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