Microsoft today patched 22 vulnerabilities in Windows and Office, including a bug in the Bluetooth technology within Vista and Windows 7 that could be used to hijack a nearby PC.
Of Tuesday's four updates, called "bulletins" by Microsoft, only one was labeled "critical" -- the most-serious rating in the company's four-step scoring system -- while the other three were marked "important," the next-most-dangerous category.
The 22 individual bugs patched today were more than in most odd-numbered months, which are typically light months for Microsoft. July's total was bested only by April's 64 and June's 34, and was tied with February's.
The standout bulletin was clearly the sole critical update, MS11-053 , researchers said today.
"It's quirky, and it's remotely exploitable," said Andrew Storms, director of security operations for nCircle Security, of the Vista and Windows update that plugs a hole in the operating systems' Bluetooth stack.
"It's at the top of our priority list," echoed Amol Sarwate, manager of Qualys' vulnerability research lab. "It could be exploited against someone using a Bluetooth mouse or headset, perhaps in a coffee shop, so it's tremendously important that people apply the patch, or if they can't do that, disable Bluetooth [on Vista and Windows 7]."
"This one's sexy," said Marcus Carey, a security researcher with Rapid7. "It's classical spy kind of stuff, being able to access [a PC] using Bluetooth when [the victim] doesn't even know you're there. All [an attacker] would have to do is go to Washington, D.C. or northern Virginia, where lots of U.S. government employees work, and sit at a Starbucks or somewhere else with free Wi-Fi."
Windows XP is not affected by the vulnerability. Although the 10-year-old operating system supports Bluetooth, Microsoft rewrote its supporting code for Vista.
Microsoft also had MS11-053 at the top of its patch chart today, but cited several caveats to explain why it believes attackers will not be able to come up with a reliable exploit in the next month.
"Your system's 48-bit Bluetooth address is not 'discoverable' by default," said Jonathan Ness, an engineer with the Microsoft Security Response Center, in a blog post today. "In the default state, an attacker must obtain your Bluetooth address another way -- either via brute forcing it or extracting it from Bluetooth traffic captured over-the-air."
The former could take an attacker hours, Ness added, while the latter requires specialized hardware that costs thousands.
Even so, experts pointed out that the Bluetooth vulnerability might be worthwhile to some attackers.
"I can see this being used in really, really targeted attacks," said Sarwate. "If someone knows you are a CEO, and may even be following you, they could exploit this to try to gain access to your system."
Jason Miller, manager of research and development with VMware's Shavlik Technologies, concurred. "You could be looking at some pretty targeted attacks," said Miller.
And Carey didn't agree with Ness' statements that attacks would be prohibitively pricey. "This would be complicated to pull off, but I wouldn't say it's expensive," he said.
Cary cited as a likely threat Project Ubertooth , which collected contributions from researchers of all kinds -- both black- and whitehats -- to mass-produce devices able to sniff out Bluetooth traffic, construct and transmit malformed data packets.
"There are thousands of these devices that were shipped," said Carey.
Storms said that although the first thing that comes to mind in a Bluetooth attack scenario is the coffee shop or public Wi-Fi hotspot, there are other subtle and plausible settings. "If someone's desk is next to a window, an attacker could target them, and have all the time in the world to brute force an attack," said Storms.
The four researchers also agreed with Microsoft that users should patch MS11-055 as soon as possible.
That update fixes a "DLL load hijacking" flaw in Visio 2003, a diagramming application that's part of the Office family.
DLL load hijacking, called "binary planting" by some security researchers, is the term used for attacks that rely on tricking applications or operating systems into loading a malicious file with the same name as a legitimate DLL, or dynamic link library.
Microsoft has issued more than a dozen DLL load-hijacking updates since last November.
Carey said that the Visio bug could also attract interest from attackers who target specific individuals.
"People who typically use Visio are high-value, often network or systems engineers," Carey argued, referring to people who would likely have other juicy information on their systems, including network administrator usernames and passwords. "These people often have the keys to the [network] kingdom."
The vulnerability could be exploited through malicious Visio documents sent via email, said Microsoft.
Microsoft also patched 15 elevation-of-privilege vulnerabilities in the Windows kernel mode drivers, 14 of them reported to the company by Tarjei Mandt, a researcher who works for Norwegian antivirus company Norman ASA. In April, Microsoft patched 30 other Mandt-submitted kernel flaws . MS11-054 plugged the 15 holes today.
July's security patches can be downloaded and installed via the Microsoft Update and Windows Update services, as well as through Windows Server Update Services.
Gregg Keizer covers Microsoft, security issues, Apple, Web browsers and general technology breaking news for Computerworld. Follow Gregg on Twitter at @gkeizer or subscribe to Gregg's RSS feed . His e-mail address is firstname.lastname@example.org .
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