Kevin BeaumontJul 12, 2023
Microsoft quietly snuck out a blog yesterday to say that Office 365 got compromised by China and used to steal emails. Thread follows. https://msrc.microsoft.com/blog/2023/07/microsoft-mitigates-china-based-threat-actor-storm-0558-targeting-of-customer-email/
Microsoft mitigates China-based threat actor Storm-0558 targeting of customer email | MSRC Blog | Microsoft Security Response Center

Microsoft mitigates China-based threat actor Storm-0558 targeting of customer email

Show threadKevin BeaumontJul 12, 2023

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

Show threadKevin BeaumontJul 12, 2023
Microsoft have not linked the blog on @msftsecintel or @msftsecresponse Twitter accounts or social media, instead linking pieces yesterday about an unrelated phishing campaign.
Show threadKevin BeaumontJul 12, 2023

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.

Show threadKevin BeaumontJul 12, 2023
Although MS haven't called this a vulnerability, haven't issued a CVE or used the term zero day.. they don't issue CVEs for cloud services, forging a token is a vulnerability, so it's a zero day.
Show threadKevin BeaumontJul 12, 2023

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

Show threadKevin BeaumontJul 12, 2023
Another element - to spot this activity, the US government used enhanced logging aka Purview Audit (Premium) logging - the US government had a huge public fight with Microsoft over this a few years ago over cost, to get access. Turns out they needed it indeed.
Show threadKevin BeaumontJul 12, 2023
Does anybody have the AppID used in the Microsoft 365 compromise? -> [email protected]
Show threadKevin BeaumontJul 12, 2023
WSJ reporting the Microsoft 365 hack was used to spy on the State Department. https://www.wsj.com/articles/chinese-hackers-spied-on-state-department-13a09f03
Chinese Hackers Breached Email of Commerce Secretary Gina Raimondo and State Department Officials

Hackers didn’t appear to gain access to national security information

WSJ
Show threadKevin BeaumontJul 12, 2023
For anybody interested - the “acquired Microsoft account (MSA) consumer signing key” used in this must have come from inside Microsoft’s internal network.
Show threadKevin BeaumontJul 12, 2023
The teams who worked on the Microsoft 365 breach of customer data are having a snow day still, I see.
Show threadKevin BeaumontJul 12, 2023

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.

Show threadKevin BeaumontJul 12, 2023

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/

Show threadKevin BeaumontJul 13, 2023
None of these would have helped, since the breach was at Microsoft’s end.
Show threadKevin BeaumontJul 13, 2023

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.

Show threadKevin BeaumontJul 13, 2023

🎶 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

Show threadKevin BeaumontJul 14, 2023
On how the USG, European govs and Microsoft have been threat hunting the MS 365 breach, per Microsoft documentation on the logs... "If a mailbox is throttled, you can probably assume there was MailItemsAccessed activity that wasn't recorded in the audit logs."
Show threadKevin BeaumontJul 14, 2023
Really good new MS blog on the MS compromise - contains IOCs etc. I'll put MSPaint.exe down. https://www.microsoft.com/en-us/security/blog/2023/07/14/analysis-of-storm-0558-techniques-for-unauthorized-email-access/
Analysis of Storm-0558 techniques for unauthorized email access | Microsoft Security Blog

Analysis of the techniques used by the threat actor tracked as Storm-0558 for obtaining unauthorized access to email data, tools, and unique infrastructure characteristics. 

Microsoft Security Blog
Show threadKevin BeaumontJul 14, 2023

“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/

Microsoft takes pains to obscure role in 0-days that caused email breach

Critics also decry Microsoft's "pay-to-play" monitoring that detected intrusions.

Ars Technica
Show threadAlan Miller  🇺🇦
@GossiTheDog “We don’t have any evidence that the actor exploited a 0day." Well perhaps they should have paid for a higher tier plan with better access to logging.
Jul 15, 2023 at 1:44amWeb