Dark Reading is part of the Informa Tech Division of Informa PLC

This site is operated by a business or businesses owned by Informa PLC and all copyright resides with them.Informa PLC's registered office is 5 Howick Place, London SW1P 1WG. Registered in England and Wales. Number 8860726.

Threat Intelligence

9/11/2020
11:45 AM
Connect Directly
Twitter
RSS
E-Mail
50%
50%

Spear-Phishers Leverage Office 365 Ecosystem to Validate Stolen Creds in Real Time

New attack technique uses Office 365 APIs to cross-check credentials against Azure Active Directory as victim types them in.

Serving as yet another proof point of the creativity with which attackers are targeting Office 365 users with new phishing schemes, Armorblox researchers yesterday detailed a new attack technique they found that validates stolen credentials in real time as the victim enters them into the login lure.

The attack in question is part of a very targeted spear-phishing campaign that was discovered operating against an executive at a top 50 American company. It works like this: Attackers send a typical credential phishing email using Amazon Simple Email Service to pass DKIM and SPF checks. Attached to the message is a bogus payment remittance report that looks like a text file with a title along the lines of "ACH Company Name." 

Opening that file automatically opens up a look-alike Office 365 sign-on page with the user's email address already pre-entered, with a message that says, "Because you're accessing sensitive info, you need to verify your password."

Related Content:

Office 365's Vast Attack Surface & All the Ways You Don't Know You're Being Exploited Through It

The Threat from the Internet—and What Your Organization Can Do About It

New on The Edge: Think You're Spending Enough on Security?

All of these steps are fairly standard, but what happens next is what differentiates this attack from others. When a victim enters a password into the fake login screen, that triggers a call to Office 365 APIs to actively validate that username/password combination against that organization's Azure Active Directory infrastructure.  

"This immediate feedback allows the attacker to respond intelligently during the attack," wrote Team Armorblox in a blog post about the attack. "The attacker is also immediately aware of a live, compromised credential and allows him to potentially ingratiate himself into the compromised account before any remediation."

If the login verification is successful, the user is redirected to zoom.com, likely as a diversionary tactic to make the process look like a benign glitch. If the authentication fails, the user is directed to login.microsoftonline.com, likely to hide the phishing attempt as a failed sign-on at the Office 365 portal.

In examining the attack, Armorblox found limited activity at the website hosting the attack. In addition, along with the timing of the lure email being sent — it was a Friday evening — the attack was carefully leveraged against that executive and organization.

"Our estimates show there have been 120-odd visits to this website globally since the beginning of June. The sparse number shows that the phishing scams are likely targeted and not spray and pray," they wrote. 

This is one example of many new and creative ways to exploit the interconnected nature of the Office 365 ecosystem through various phishing and business email compromise (BEC) schemes. 

For example, in late July Abnormal Security researchers reported an attack concocted to look like automated Sharepoint messages to snag employee credentials. And in early August researchers with Trend Micro reported a wave of BEC campaigns that have been targeting the Office 365 accounts of business executives since March. Meantime, a study released by Ironscales several weeks ago found some 9,500 different fake Microsoft login pages lurking online, all connected to different campaigns targeting Office 365.

At Black Hat USA this year, researchers Josh Madeley and Doug Bienstock presented on a range of different kind of tactics, techniques, and procedures (TTP) used by attackers against Office 365. They said the ecosystem has grown increasingly interesting to attackers as more enterprises fully embrace it for a range of different applications that reach far beyond email.  

"A lot of organizations have lifted their on-premise Exchange environment into the cloud without much consideration or awareness of the new risks and attacker vectors this exposes them to," according to Bienstock, in a separate interview. He explained that the combination of different valuable productivity environments like Outlook, OneDrive, SharePoint, and Teams open up a huge volume of sensitive data in a consolidated cloud platform. It's a vector ripe for attack, he pointed out.

In a recent Dark Reading News Desk interview during Black Hat, Madeley somewhat presaged the attack described by Armorblox by explaining that Azure Active Directory is a feature often overlooked as a threat vector for Office 365 organizations.

"It is, for most organizations, the authentication provider for their employees," he explained. "So if an attacker has access to that, they have access to sites that are integrated into active directory that are federated with Azure." 

 

Ericka Chickowski specializes in coverage of information technology and business innovation. She has focused on information security for the better part of a decade and regularly writes about the security industry as a contributor to Dark Reading.  View Full Bio
 

Recommended Reading:

Comment  | 
Print  | 
More Insights
Comments
Newest First  |  Oldest First  |  Threaded View
HiteshVectra
50%
50%
HiteshVectra,
User Rank: Author
9/11/2020 | 12:56:58 PM
The balance between securing all things O365 and securing the hybrid cloud
To add to the list, we have seen an increase in attacks via Teams. The first being attackers using a compromised account to add an external account to be a member of an existing O365 Teams account.  The other is attackers tricking users into installing applications into Teams environments which may undermine existing security controls, such as multi-factor authentication (MFA), and enable malicious action on behalf of the authorizing user.  So while the threat landscape seems to increase on a daily basis, we see customers putting more focus on identifying and stopping attacks in their hybrid cloud since that is typically the destination of the breach. And while there are ways to secure the entire threat landscape, SOCs typically don't have the capacity to secure every single thing nor the hours in a day to do so. 
NSA Appoints Rob Joyce as Cyber Director
Dark Reading Staff 1/15/2021
Vulnerability Management Has a Data Problem
Tal Morgenstern, Co-Founder & Chief Product Officer, Vulcan Cyber,  1/14/2021
Register for Dark Reading Newsletters
White Papers
Video
Cartoon
Current Issue
2020: The Year in Security
Download this Tech Digest for a look at the biggest security stories that - so far - have shaped a very strange and stressful year.
Flash Poll
Assessing Cybersecurity Risk in Today's Enterprises
Assessing Cybersecurity Risk in Today's Enterprises
COVID-19 has created a new IT paradigm in the enterprise -- and a new level of cybersecurity risk. This report offers a look at how enterprises are assessing and managing cyber-risk under the new normal.
Twitter Feed
Dark Reading - Bug Report
Bug Report
Enterprise Vulnerabilities
From DHS/US-CERT's National Vulnerability Database
CVE-2020-27852
PUBLISHED: 2021-01-20
A stored Cross-Site Scripting (XSS) vulnerability in the survey feature in Rocketgenius Gravity Forms before 2.4.21 allows remote attackers to inject arbitrary web script or HTML via a textarea field. This code is interpreted by users in a privileged role (Administrator, Editor, etc.).
CVE-2021-3137
PUBLISHED: 2021-01-20
XWiki 12.10.2 allows XSS via an SVG document to the upload feature of the comment section.
CVE-2020-27850
PUBLISHED: 2021-01-20
A stored Cross-Site Scripting (XSS) vulnerability in forms import feature in Rocketgenius Gravity Forms before 2.4.21 allows remote attackers to inject arbitrary web script or HTML via the import of a GF form. This code is interpreted by users in a privileged role (Administrator, Editor, etc.).
CVE-2020-27851
PUBLISHED: 2021-01-20
Multiple stored HTML injection vulnerabilities in the "poll" and "quiz" features in an additional paid add-on of Rocketgenius Gravity Forms before 2.4.21 allows remote attackers to inject arbitrary HTML code via poll or quiz answers. This code is interpreted by users in a privile...
CVE-2020-13134
PUBLISHED: 2021-01-20
Tufin SecureChange prior to R19.3 HF3 and R20-1 HF1 are vulnerable to stored XSS. The successful exploitation requires admin privileges (for storing the XSS payload itself), and can exploit (be triggered by) admin users. All TOS versions with SecureChange deployments prior to R19.3 HF3 and R20-1 HF1...