Google, Microsoft work together for a year to figure out new type of Windows flaw

Researcher finds building blocks for privilege escalation: Can they be assembled to create a flaw?

Google, Microsoft work together for a year to figure out new type of Windows flaw

Enlarge (credit: Marco Verch / Flickr)

One of the more notable features of Google Project Zero's (GPZ) security research has been its 90-day disclosure policy. In general, vendors are given 90 days to address issues found by GPZ, after which the flaws will be publicly disclosed. But sometimes understanding a flaw and developing fixes for it takes longer than 90 days—sometimes, much longer, such as when a new class of vulnerability is found. That's what happened last year with the Spectre and Meltdown processor issues, and it has happened again with a new Windows issue.

Google researcher James Forshaw first grasped that there might be a problem a couple of years ago when he was investigating the exploitability of another Windows issue published three years ago. In so doing, he discovered the complicated way in which Windows performs permissions checks when opening files or other secured objects. A closer look at the involved parts showed that there were all the basic elements to create a significant elevation of privilege attack, enabling any user program to open any file on the system, regardless of whether the user should have permission to do so. The big question was, could these elements be assembled in just the right way to cause a problem, or would good fortune render the issue merely theoretical?

The basic rule is simple enough: when a request to open a file is being made from user mode, the system should check that the user running the application that's trying to open the file has permission to access the file. The system does this by examining the file's access control list (ACL) and comparing it to the user's user ID and group memberships. However, if the request is being made from kernel mode, the permissions checks should be skipped. That's because the kernel in general needs free and unfettered access to every file.

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Microsoft’s latest security service uses human intelligence, not artificial

Computers are good at processing vast amounts of data, but humans still have their uses.

Microsoft security experts monitoring the world, looking for hackers.

Enlarge / Microsoft security experts monitoring the world, looking for hackers. (credit: Microsoft)

Microsoft has announced two new cloud services to help administrators detect and manage threats to their systems. The first, Azure Sentinel, is very much in line with other cloud services: it's dependent on machine learning to sift through vast amounts of data to find a signal among all the noise. The second, Microsoft Threat Experts, is a little different: it's powered by humans, not machines.

Azure Sentinel is a machine learning-based Security Information and Event Management that takes the (often overwhelming) stream of security events—a bad password, a failed attempt to elevate privileges, an unusual executable that's blocked by anti-malware, and so on—and distinguishes between important events that actually deserve investigation and mundane events that can likely be ignored.

Sentinel can use a range of data sources. There are the obvious Microsoft sources—Azure Active Directory, Windows Event Logs, and so on—as well as integrations with third-party firewalls, intrusion-detection systems, endpoint anti-malware software, and more. Sentinel can also ingest any data source that uses ArcSight's Common Event Format, which has been adopted by a wide range of security tools.

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Google: Software is never going to be able to fix Spectre-type bugs

Researchers also devise a Spectre-like attack with no known mitigation.

Google: Software is never going to be able to fix Spectre-type bugs

Enlarge (credit: Aurich Lawson / Getty Images)

Researchers from Google investigating the scope and impact of the Spectre attack have published a paper asserting that Spectre-like vulnerabilities are likely to be a continued feature of processors and, further, that software-based techniques for protecting against them will both impose a high performance cost. In any case, the researchers continue, the software will be inadequate—some Spectre flaws don't appear to have any effective software-based defense. As such, Spectre is going to be a continued feature of the computing landscape, with no straightforward resolution.

The discovery and development of the Meltdown and Spectre attacks was undoubtedly the big security story of 2018. First revealed last January, new variants and related discoveries were made throughout the rest of the year. Both attacks rely on discrepancies between the theoretical architectural behavior of a processor—the documented behavior that programmers depend on and write their programs against—and the real behavior of implementations.

Specifically, modern processors all perform speculative execution; they make assumptions about, for example, a value being read from memory or whether an if condition is true or false, and they allow their execution to run ahead based on these assumptions. If the assumptions are correct, the speculated results are kept; if it isn't, the speculated results are discarded and the processor redoes the calculation. Speculative execution is not an architectural feature of the processor; it's a feature of implementations, and so it's supposed to be entirely invisible to running programs. When the processor discards the bad speculation, it should be as if the speculation never even happened.

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Mandatory update coming to Windows 7, 2008 to kill off weak update hashes

Microsoft is phasing out SHA-1 hashes on its patches.

Mandatory update coming to Windows 7, 2008 to kill off weak update hashes


Windows 7 and Windows Server 2008 users will imminently have to deploy a mandatory patch if they want to continue updating their systems, as spotted by Mary Jo Foley.

Currently, Microsoft's Windows updates use two different hashing algorithms to enable Windows to detect tampering or modification of the update files: SHA-1 and SHA-2. Windows 7 and Server 2008 verify the SHA-1 patches; Windows 8 and newer use the SHA-2 hashes instead. March's Patch Tuesday will include a standalone update for Windows 7, Windows Server 2008 R2, and WSUS to provide support for patches hashed with SHA-2. April's Patch Tuesday will include an equivalent update for Windows Server 2008.

The SHA-1 algorithm, first published in 1995, takes some input and produces a value known as a hash or a digest that's 20 bytes long. By design, any small change to the input should produce, with high probability, a wildly different hash value. SHA-1 is no longer considered to be secure, as well-funded organizations have managed to generate hash collisions—two different files that nonetheless have the same SHA-1 hash. If a collision could be generated for a Windows update, it would be possible for an attacker to produce a malicious update that nonetheless appeared to the system to have been produced by Microsoft and not subsequently altered.

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