Last week, Apple released macOS Big Sur and the rollout was anything but smooth. The mass upgrade caused the Apple servers responsible for checking if a user opens an app not downloaded from the App Store to slow to a crawl. Apple eventually fixed the problem, “but concerns about paralyzed Macs were soon replaced by an even bigger worry — the vast amount of personal data Apple, and possibly others, can glean from Macs performing certificate checks each time a user opens an app that didn’t come from the App Store,” writes Dan Goodin via Ars Technica. From the report: Before Apple allows an app into the App Store, it must first pass a review that vets its security. Users can configure the macOS feature known as Gatekeeper to allow only these approved apps, or they can choose a setting that also allows the installation of third-party apps, as long as these apps are signed with a developer certificate issued by Apple. To make sure the certificate hasn’t been revoked, macOS uses OCSP — short for the industry standard Online Certificate Status Protocol — to check its validity. […] Somehow, the mass number of people upgrading to Big Sur on Thursday seems to have caused the servers at to become overloaded but not fall over completely. The server couldn’t provide the all clear, but it also didn’t return an error that would trigger the soft fail. The result was huge numbers of Mac users left in limbo. The post Your Computer Isn’t Yours was one of the catalysts for the mass concern. It noted that the simple HTML get-requests performed by OCSP were unencrypted. That meant that not only was Apple able to build profiles based on our minute-by-minute Mac usage, but so could ISPs or anyone else who could view traffic passing over the network. (To prevent falling into an infinite authentication loop, virtually all OCSP traffic is unencrypted, although responses are digitally signed.) Fortunately, less alarmist posts like this one provided more helpful background. The hashes being transmitted weren’t unique to the app itself but rather the Apple-issued developer certificate. That still allowed people to infer when an app such as Tor, Signal, Firefox, or Thunderbird was being used, but it was still less granular than many people first assumed. The larger point was that, in most respects, the data collection by wasn’t much different from the information that already gets transmitted in real time through OCSP every time we visit a website. […] In short, though, the takeaway was the same: the potential loss of privacy from OCSP is a trade-off we make in an effort to check the validity of the certificate authenticating a website we want to visit or a piece of software we want to install. In an attempt to further assure Mac users, Apple on Monday published this post. It explains what the company does and doesn’t do with the information collected through Gatekeeper and a separate feature known as notarization, which checks the security even of non-App Store apps. The post went on to say that in the next year, Apple will provide a new protocol to check if developer certificates have been revoked, provide “strong protections against server failure,” and present a new OS setting for users who want to opt out of all of this. […] People who don’t trust OCSP checks for Mac apps can turn them off by editing the Mac hosts file. Everyone else can move along.

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