Breaking, Misc

Change Your BLE Passkey Like You Change Your Underwear

Using a static passkey for Bluetooth Low Energy pairing is insecure. Recent versions of the Bluetooth specification contain an explicit warning about this. However, in practice, we often see static passkeys being used. Moreover, there are no public implementations of proofs-of-concept that can practically show why using a static passkey is an issue. This is why we implemented one.

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Analysis of HSTS Caches of Different Browsers

The Reason

I recently stumbled upon a strange behavior in my Firefox: I visited an HTTPS-enabled website that I had visited before and saw that my Firefox connected insecurely via HTTP. I found that strange because nowadays, most websites set the HSTS header, which is supposed to force the browser to connect via HTTPS. I checked whether this website set the HSTS header – and it did. This means my Firefox was ignoring/forgetting about the HSTS header right after my visit. Continue reading “Analysis of HSTS Caches of Different Browsers”

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Breaking, Misc

Attack llvmpipe Graphics Driver from Chromium

In this post, we are discussing a bug we came across in Mesas llvmpipe Gallium3D graphics driver. This bug was accessible through Chromium’s WebGL implementation and can provide control of the program counter (pc) within Chromium’s GPU process if llvmpipe is used. Llvmpipe is a software rasterizer that is used on Linux if no hardware acceleration (graphics card) is available. This is a pretty rare edge case as llvmpipe has no widespread use. An estimate by Google is that approx 0.06% of the Chromium users are affected by this. However, as this is a simple but valid Chromium bug, we want to give you a quick walkthrough. The issue is tracked as CVE-2021-21153 and was fixed in February 2020.

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BSI veröffentlicht Hardening Guide, Protokollierungs-Empfehlung und zugehörige GPOs für Windows 10 im Rahmen der SiSyPHuS-Studie

Wir freuen uns, dass das Bundesamt für Sicherheit in der Informationstechnik (BSI) im Rahmen des gemeinsam mit ERNW durchgeführten SiSyPHuS Win10-Projekts (Studie zu Systemintegrität, Protokollierung, Härtung und Sicherheitsfunktionen in Windows 10) heute (ca. 10 Uhr) die nächsten drei Arbeitspakete veröffentlicht:

  • Empfehlung zur Härtung von Windows 10 mit Bordmitteln
  • Empfehlung zur Konfiguration der Protokollierung in Windows 10
  • Gruppenrichtlinien zu den Konfigurationsempfehlungen für Härtung und Protokollierung für Windows 10

In den Dokumenten finden sich unterschiedliche Empfehlungen für Domänenmitglieder (mit normalem und mit hohem Schutzbedarf) und Einzelplatzrechner. Die Dokumente bauen auf den Empfehlungen von Microsofts Security Baseline und dem CIS Benchmark für Windows 10 auf und ergänzen diese in von Microsoft und CIS nicht betrachteten Bereichen oder modifizieren sie dort, wo es aus Erfahrung von ERNW im Hardening von Windows-Systemen sinnvoll ist.

Sie finden die Dokumente hier.

Wir hoffen, damit zur Sicherheit von Windows-Umgebungen beitragen zu können, und wünschen Ihnen viel Spaß bei der Lektüre!


German Federal Office for Information Security (BSI) Publishes Hardening Guideline, Logging Guideline And Related GPOs for Windows 10

We are happy to announce that today the BSI publishes several documents that ERNW created as part of the long-term SiSyPHuS Win10-Project (ger: “Studie zu Systemintegrität, Protokollierung, Härtung und Sicherheitsfunktionen in Windows 10”, en: “Study on System Integrity, Logging, Hardening and Security relevant Functionality in Windows 10”):

  • Hardening Guideline
  • Logging Guideline
  • GPOs for the Guidelines

The guidelines are built on recommendations from Microsoft´s Security Baseline, CIS Benchmarks and ERNW´s expertise.

You  can find the documents and GPOs here.

Let’s make the Windows world a safer place, and have fun reading!



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Of Corona, Buggy Audio Drivers and Industrial Espionage

The Situation

Last year, the CISO of a customer sent me a laptop for analysis. The reason was that he feared the company could have been victim of industrial espionage. Starting in spring 2020, the IT help desk got several employee laptops with full hard drives, caused by a huge amount of audio recordings. The audio files contained recordings even of highly sensitive telephone conferences. An automated scan on all employee computers for such audio recordings showed that about 300 devices were affected. Continue reading “Of Corona, Buggy Audio Drivers and Industrial Espionage”

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Breaking, Misc

fpicker: Fuzzing with Frida


In this post, I will introduce fpicker. Fpicker is a Frida-based coverage-guided, mostly in-process, blackbox fuzzing suite. Its most significant feature is the AFL++ proxy mode which enables blackbox in-process fuzzing with AFL++ on platforms supported by Frida. In practice, this means that fpicker enables fuzzing binary-only targets with AFL++ on potentially any system that is supported by Frida. For example, it allows fuzzing a user-space application on the iOS operating system, such as the Bluetooth daemon bluetoothd – which was part of the original motivation to implement fpicker.
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ERNW Whitepaper 71 – Analysis of Anti-Virus Software Quarantine Files

I am glad to announce the release of the ERNW whitepaper 71 containing information about quarantine file formats of different AV software vendors. It is available here.

Anti-Virus Software

I took quarantine files from real-life incidents and created some in a lab environment. Afterwards I tried to identify metadata, like timestamps, path names, malware names, and the actual malicious file in the quarantine files. One goal was to use this information to support our incident analyses: Using the results, we can now easily create timelines showing information about quarantined files, extract the detected malware, and sometimes even find information about processes that created the malicious files. Continue reading “ERNW Whitepaper 71 – Analysis of Anti-Virus Software Quarantine Files”

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Having Fun with Google MDM Solution

It’s Friday, you managed to escape for a couple of hours from a busy working day to see a doctor. Now you have to wait in a boring waiting room at the clinic until it’s your turn to see her majesty. What would you like to do in this time? Answer pending business emails, get lost in social media, or choose a new theme to make your iPhone look awesome?  What about: all of the above? It’s nice to have everything on your iPhone: MDM enrollment to access business data, in addition to jailbreak for device freedom. However, MDM solutions ban jailbroken devices, because they are not secure enough to handle sensitive business data. And so, cat and mouse games of jailbreak detection/bypass between MDM solutions and some users develop.

In this blogpost, I highlight how this cat and mouse game with Google’s MDM solution “Google Endpoint Management” is currently going. First, I explain how to bypass jailbreak detection of Google’s MDM solution. Then I show how to manipulate MDM enforced policies on your MDM-enrolled jailbroken device. Since these actions have negative impacts on your device’s security, we’ll also discuss how attackers can exploit this insecure setup to steal business data.

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