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Computerworld - Apple missed a golden opportunity to lock down Snow Leopard when it again failed to fully implement security technology that Microsoft perfected nearly three years ago in Windows Vista, a noted Mac researcher said today.

Dubbed ASLR, for address space layout randomization, the technology randomly assigns data to memory to make it tougher for attackers to determine the location of critical operating system functions, and thus make it harder for them to craft reliable exploits.

"Apple didn't change anything," said Charlie Miller, of Baltimore-based Independent Security Evaluators, the co-author of The Mac Hacker's Handbook, and winner of two consecutive "Pwn2own" hacker contests. "It's the exact same ASLR as in Leopard, which means it's not very good."

Two years ago, Miller and other researchers criticized Apple for releasing Mac OS X 10.5, aka Leopard, with half-baked ASLR that failed to randomize important components of the OS, including the heap, the stack and the dynamic linker, the part of Leopard that links multiple shared libraries for an executable.

Miller was disappointed that Apple didn't improve ASLR from Leopard to Snow Leopard. "I hoped Snow Leopard would do full ASLR, but it doesn't," said Miller. "I don't understand why they didn't. But Apple missed an opportunity with Snow Leopard."

Even so, Miller said, Apple made several moves that did improve Mac OS X 10.6's security. Two that stand out, he said, were its revamp of QuickTime and additions to DEP (data execution prevention), another security feature used in Windows Vista.

"Apple rewrote a bunch of QuickTime," said Miller, "which was really smart, since it's been the source of lots of bugs in the past." That's not surprising, since QuickTime supports scores of file formats, historically its weak link. Last week, in fact, Apple patched four critical QuickTime vulnerabilities in the program's parsing of various file formats.