RansomWhere? adds Mac App Store trust logic
Objective-See details how RansomWhere? will verify Mac App Store receipts to reduce false positives, referencing the KeRanger ransomware as a signed-but-non-App-Store example.
Sourceobjective-see.org — open the original
What to check
- Applies to
- Whether this concerns you is not assessed; the names the report mentions are listed below.
- Date
- The source gives no publication date; the date shown is the day Vorant added the brief.
This is a technical blog post from Objective-See explaining how to programmatically verify whether a macOS application originated from Apple's Mac App Store by validating its embedded receipt. The author walks through code using Apple's Security framework APIs (SecStaticCodeCheckValidity, CMSDecoder, SecAsn1Coder) to check code signing, locate and decode the app receipt, and validate bundle ID, version, and SHA1 hash matches against the receipt data.
The motivation is to improve RansomWhere?, a generic OS X ransomware detection tool, by allowing version 1.1 to trust processes backed by legitimate Mac App Store applications, thereby reducing false positives. The author references the KeRanger ransomware as an example of malware that was signed with a legitimate Apple Developer ID but was not distributed via the App Store, demonstrating why code-signing checks alone are insufficient and receipt validation is needed.
This is an informational/educational research post with no active threat or campaign; it discusses defensive tooling development rather than an ongoing attack. Severity is low as this is a research/tooling article, not an active threat.
Mentioned in this report
Source reporting: https://objective-see.org/blog/blog_0x10.html
Free public brief. The indicators are in the app with a free account, no card. Slack alerts on the vendors you run come with the paid plans, and a new account gets three days of them.
What this brief leaves out
This page is the free tier: the write-up, the severity, the names. In the app the same report carries its extracted indicators and live profiles of the malware it names. The paid plans add the security research and news reporting the free tier leaves out.
It sits in a corpus of 16,436 reports from 149 sources, 661 of them written in the last seven days, and it grows through the day.
A new account starts with three days of all of it, no card, then keeps the government and CERT reporting free. Slack alerts are a paid-plan feature: name the vendors you run and Slack hears about the reports that touch them, not the rest of the week's. Nothing is charged unless you subscribe.
Create a free account What it costs