How can you prevent malicious programmers from finding flaws in the code to exploit security problems?
You might as well ask how you stop someone breaking into your home. You want to make it difficult to do (by adding locks on the doors), make it transparent when it does (by adding an alarm), and ensure a prompt response (so the alarm alerts the police). The idea is to disincentivize that behavior. We’re doing the same on the Second Life Grid, which as you might imagine has security, constant monitoring, and a 24 hour response team. But, ultimately, if someone is determined to break in, has access to the right resources and skills, and enough time – they may well succeed. To that extent, the Second Life Grid is as much at risk as any other online business.