Windows 8: A secure OS for government?

LAS VEGAS — Government agencies pondering whether to migrate to the latest version of the Windows operating system due out later this year got some good news from researchers at the Black Hat Briefings.

Microsoft has significantly reduced the attack surface of Windows 8, raising the bar for attackers targeting the new version of the operating system, said Chris Valasek, a senior security researcher at Coverity who has been examining early releases of the new operating system.

“They did a fantastic job of closing the security deficiencies that we found previously, in Windows 7 especially,” Valasek said.


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Valasek and Tarjei Mandt, senior vulnerability researcher at Azimuth Security, have focused their research on the memory manager in the new OS. They presented their findings July 25 in a talk on Windows 8 Heap Internals.

So should agencies make the leap to Windows 8?

“From a strictly security standpoint, moving to Windows 8 seems like a good move,” Valasek said. But security is not the only consideration, he noted. The government environment contains many custom applications that are not plug-and-play and he could not say how well the new Windows would work with government-only software.

Although it is a small part of the operating system, Valasek said that the time and effort put into improving security in the heap manager bodes well for the operating system as a whole.

“I think that has things to say for the overall security architecture,” he said. “I don’t think anyone from Microsoft will tell you that attacking the heap is impossible, but it will take skilled people to attack those kinds of things. I wouldn’t want to be tasked with creating a heap exploit for Windows 8.”

Microsoft earlier in July announced that Windows 8 would be released October 26.

Windows 8, which contains the significantly updated Metro user interface, is eagerly awaited and there is plenty of room in the current OS market for its adoption. Microsoft’s Vista operating system peaked at only about 30 percent of the OS market. That lack of adoption means that, despite the subsequent success of Windows 7, there still is a large installed base of older Windows versions ready for migration.

According to StatCounter Global Stats, Windows 7 passed XP in October 2011 with about 40 percent of the market, and Win 7 held about 50 percent of the market in June 2012. But XP still accounts for about 30 percent and Vista about 8 percent. Some government workers attending Black Hat said that the share of older operating systems in government could be higher because budget constraints have delayed some upgrades.

Valasek has been analyzing Windows 8 since the release of the developer’s version last fall, and he and Mandt now are looking at the Consumer Preview that was released in February.

Despite the new Metro interface that is intended to provide a common look and feel across both mobile and desktop platforms, a lot of the code in Windows 8 has carried over from earlier versions back to Vista, and the new release has benefited from it, Valasek said.

“People had little good to say of Vista, but the code maturity is really getting there,” he said.

It also has benefited from a maturing culture at Microsoft, he said. “Over the years they have hired a lot of security people on both sides, offensive and defensive. That has really helped. It is no longer just in-house Microsoft thinking.”

The OS heap dynamically allocates memory to applications as needed, freeing the blocks for reuse when they no longer are needed. Heap overflow exploits can corrupt program data in allocated blocks, allowing it to be overwritten, which can permit execution of arbitrary code. Referencing memory after it has been freed for reuse also can cause programs to crash and corrupt data.

To take advantage of this, an attacker needs to know where to look for the memory blocks being allocated. Windows 8 randomizes allocation, making it difficult to target the blocks.

Valasek said there is more security in the Windows 8 heap manager than in all previous versions of Windows. He described the security advances from Windows XP to Windows 7 as “leaps and bounds,” and said the advance from version 7 to 8 is just as great.

Valasek published a heap exploit technique for Windows 7, “so I was pretty sure they were going to fix it,” he said. “But they went above and beyond. We were both a little surprised at how much security was added.”

 

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