They used Outlook Web App - runs the Exchange Server codebase btw - to craft tokens to bypass auth.

There's some clever wording in blog around only impacting OWA. OWA is a part of Microsoft 365 and Exchange Online.

The problem was discovered by the US Government and reported to Microsoft. https://edition.cnn.com/2023/07/12/politics/china-based-hackers-us-government-email-intl-hnk/index.html

This one looks like a huge mistake, a consumer MSA key (managed end to end by Microsoft - there's no external logs) was able to forge any Azure AD key.

It's only become public it appears as the US Government told Microsoft, which forces public disclosure.

CISA's advisory on the Microsoft 365 compromise is wayyyyyyyyyyy better than the Microsoft advisory - contains actionable hunting and logging information. Kinda nuts that the US Government are providing better information about Microsoft than Microsoft.

https://www.cisa.gov/sites/default/files/2023-07/aa23-193a_joint_csa_enhanced_monitoring_to_detect_apt_activity_targeting_outlook_online.pdf

Okay - I found a victim org.

The situation for them is 😬

MS are going to have to release more info, methinks.. or I crank out the blog writing.

Really good Washington Post piece on the breach of Microsoft 365’s email service.

- hackers accessed customer emails for a month
- Microsoft didn’t notice
- USG had to tell them
- The access to generate tokens very likely came from MS being hacked and not realising

https://archive.is/2023.07.12-230927/https://www.washingtonpost.com/national-security/2023/07/12/microsoft-hack-china/

Talked to another impacted victim org in the Microsoft 365 hack, they basically got no actionable info from MS. Basically ‘lol you got hacked’ with wordsmithing and padding. 👀😬

I think I’m going to post hunting queries for this with an MS Paint logo.

🎶 regulation 🎶

I agree with CISA here (and have publicly for years) - security access logs for customers own services shouldn't be locked behind E5 per user licensing.

Yes, it will cost Microsoft money in upsell. They're more profitable than a large portion of the UK economy; they can afford it.

I should also point out the reason Microsoft was able to tell orgs specifically that they'd be targeted even when they didn't have E5 is MS already store the logs anyway.

https://archive.ph/MFnxP

“We don’t have any evidence that the actor exploited a 0day." say Microsoft. Their first blog on this says “exploit” - so are MS saying they don’t patch vulnerabilities in their cloud? 🤔

Their latest blog also says “This was made possible by a validation error in Microsoft code” - which is a vulnerability. Which is a 0day as it was under exploitation before Microsoft knew of it existing.

Microsoft lying to media and customers is not a good look.

https://arstechnica.com/security/2023/07/microsoft-takes-pains-to-obscure-role-in-0-days-that-caused-email-breach/

All it took was Exchange Online in GCC and GCC High getting breached

Non-E5 users to get some security log availability finally.

https://www.wsj.com/articles/microsoft-to-offer-some-cybersecurity-tools-free-after-suspected-china-hack-6db94221

More details about the Microsoft 365 Exchange Online breach in this article.

Although not stated, orgs are struggling to understand the scope of the breach due to audit log limits on MailItemsAccessed - it stops recording after 1k items. https://www.wsj.com/articles/u-s-ambassador-to-china-hacked-in-china-linked-spying-operation-f03de3e4

Just to loop this thread into this thread - I took a look at the attack path used in the M365 customer data breach.

A key part of the attack chain was documented by Microsoft at BlackHat in 2019.

https://cyberplace.social/@GossiTheDog/110736594147931759

Wiz have an in-depth look at what they think happened at Microsoft over the Microsoft 365 breach.

They nail a new detail - one of the 'acquired' signing keys expired in 2021, but apparently it was still valid in Microsoft's cloud services. https://www.wiz.io/blog/storm-0558-compromised-microsoft-key-enables-authentication-of-countless-micr

YOU MUST ONLY READ THE OFFICIAL BLOGS

there is no breach
there is no vulnerability
there are no zero days
*jedi wave*

https://therecord.media/microsoft-disputes-report-on-chinese-hacking

The Microsoft write up on how Microsoft 365 got owned to steal customer emails is out. It’s really good and honest from a technical level I think, if you’ve been following the details closely. Top points to the US Gov for forcing public disclosure originally btw.

https://msrc.microsoft.com/blog/2023/09/results-of-major-technical-investigations-for-storm-0558-key-acquisition/

There’s a pretty good look at unanswered questions the MSRC blog on the Microsoft 365 customer data breach in this: https://arstechnica.com/security/2023/09/hack-of-a-microsoft-corporate-account-led-to-azure-breach-by-chinese-hackers/

Unsurprisingly MS aren’t using words like ‘breach’, ‘vulnerability’ etc when clearly it was both. It’s almost like there’s misaligned incentives.

Other obvious issues include a compromise in 2021 where the threat actor took process dumps etc but nobody checked what they were doing (you live and learn etc), no HSMs etc. Assume MS are compromised.

This TechCrunch piece has one extra detail not in the MSFT blog on the Microsoft 365 data breach - access was gained via session token theft.

To expand, Microsoft use Azure AD MFA, which has a problem with session token theft. https://techcrunch.com/2023/09/08/microsoft-hacker-china-government-storm-0558/

US State Department have gone on the record about how they found the Microsoft 365 data breach.

They set up a detection rule called Big Yellow Taxi two years ago to look for unknown AppIDs in OfficeActivity, which ultimately saved Microsoft’s ass.

https://www.politico.com/news/2023/09/15/digital-tripwire-helped-state-uncover-chinese-hack-00115973