1. Microsoft lost a general login key to its entire email system which enabled China to siphon off ~60,000 emails from the US State Department, the US ambassador to China, and other US government officials.

But what made this hack possible? 👇

🧵2/7

2. The old signing key used by the Chinese hackers to break into the system should have been disabled in 2016 already.

🧵3/7

3. Microsoft should have switched from manual to an automated key rotation - which would have automatically disabled the old key - but didn't.

🧵4/7

4. The key worked like a backdoor to consumer and business networks, which is in violation of security protocols.

🧵5/7

5. One engineer from a firm acquired by Microsoft in 2020 was working on a compromised laptop and in 2021 accessed the corporate network from that machine. It's not certain that this laptop was the root cause, but Microsoft published an update in March 2024 which stated a “compromised engineering account” is the “leading hypothesis” for the cause of the breach.

🧵6/7

6. Instead of letting this compromise go unnoticed, Microsoft should have run a proper security assessment of the firm's network after its acquisition - which it didn't.

More on this hack and what the US government has to say about it: tuta.com/blog/microsoft-china-…

🧵7/7

US government asks Microsoft to get its security right - before adding any new features.

China's Microsoft hack shows why security must always be prioritized over features and why there must not be a general key that can be used as a "backdoor".

^Tutanota