Russia-state hackers exploited a weak password to compromise Microsoft’s company network and accessed emails and paperwork that belonged to senior executives and workers working in safety and authorized groups, Microsoft mentioned late Friday.

The assault, which Microsoft attributed to a Kremlin-backed hacking group it tracks as Midnight Blizzard, is a minimum of the second time in as a few years that failures to comply with primary safety hygiene has resulted in a breach that has the potential to hurt clients. One paragraph in Friday’s disclosure, filed with the Securities and Trade Fee, was gobsmacking:

Starting in late November 2023, the risk actor used a password spray assault to compromise a legacy non-production check tenant account and achieve a foothold, after which used the account’s permissions to entry a really small proportion of Microsoft company electronic mail accounts, together with members of our senior management crew and workers in our cybersecurity, authorized, and different features, and exfiltrated some emails and connected paperwork. The investigation signifies they have been initially focusing on electronic mail accounts for data associated to Midnight Blizzard itself. We’re within the means of notifying workers whose electronic mail was accessed.

Microsoft didn’t detect the breach till January 12, precisely every week earlier than Friday’s disclosure. Microsoft’s account raises the prospect that the Russian hackers had uninterrupted entry to the accounts for so long as two months.

A translation of the 93 phrases quoted above: A tool inside Microsoft’s network was protected by a weak password with no type of two-factor authentication employed. The Russian adversary group was in a position to guess it by peppering it with beforehand compromised or generally used passwords till they lastly landed on the suitable one. The risk actor then accessed the account, indicating that both 2FA wasn’t employed or the safety was in some way bypassed.

Moreover, this “legacy non-production check tenant account” was in some way configured in order that Midnight Blizzard may pivot and achieve entry to among the firm’s most senior and delicate worker accounts.

As Steve Bellovin, a pc science professor and affiliate regulation prof at Columbia College with a long time of expertise in cybersecurity, wrote on Mastodon:

Lots of fascinating implications right here. A profitable password spray assault suggests no 2FA and both reused or weak passwords. Entry to electronic mail accounts belonging to “senior management… cybersecurity, and authorized” groups utilizing simply the permissions of a “check tenant account” suggests that somebody gave that check account wonderful privileges. Why? Why wasn’t it eliminated when the check was over? I additionally observe that it took Microsoft about seven weeks to detect the assault.

Whereas Microsoft mentioned that it wasn’t conscious of any proof that Midnight Blizzard gained entry to buyer environments, manufacturing techniques, supply code, or AI techniques, some researchers voiced doubts, notably about whether or not the Microsoft 365 service is perhaps or have been inclined to comparable assault strategies. One of many researchers was Kevin Beaumont, who has had a protracted cybersecurity profession that has included a stint working for Microsoft. On LinkedIn, he wrote:

Microsoft employees use Microsoft 365 for electronic mail. SEC filings and blogs with no particulars on Friday night time are nice.. however they’re going to need to be adopted with precise element. The age of Microsoft doing tents, incident code phrases, CELA’ing issues and pretending MSTIC sees every part (risk actors have Macs too) are over — they should do radical technical and cultural transformation to retain belief.

CELA is brief for Company, Exterior, and Authorized Affairs, a gaggle inside Microsoft that helps draft disclosures. MSTIC stands for the Microsoft Risk Intelligence Middle.