A new phishing attack begins with a scam email disguised as an automated message from Microsoft SharePoint, Abnormal Security observed on Monday, July 27. Those responsible for the attack do not address the email to any specific employee within the targeted organization. This tactic makes it more likely that at least one employee will fall for the scam. Therefore, malicious actors can use their credentials to gain access to sensitive information.
The body of the email uses generic language to inform the recipient they have received a message containing ‘important documents.’ It also includes the name of the target company to add a sense of legitimacy. Signed by the ‘SharePoint Team,’ the email instructs the recipient to click on an embedded ‘View Documents’ link.
The link doesn’t send the recipient to SharePoint as promised, however. Instead, it employs a series of redirects to send them to a landing page identical to a secure SharePoint file. This landing page displays the official Microsoft and SharePoint logos to convince the user they can trust the site. If they click the ‘Click Here to Download’ button, they are given access to a PDF file.
In the event they click the button, the site redirects the user to a form designed to steal their Microsoft account credentials. In other instances, the landing page downloads a PDF document that then directs them to another malicious site.
Other SharePoint-Related Attacks
The attack described above isn’t the first instance of malicious activity involving SharePoint. In August 2018, Avanan revealed it had detected a scam email containing a link to a SharePoint file. Clicking on the email’s embedded link caused the computer to open a SharePoint file that impersonated an access request to a OneDrive file. Once the user clicked the ‘Access Document’ hyperlink, that SharePoint file redirected them to a landing page designed to steal their Office 365 credentials.
About a year later, Naked Security detected a phishing email notifying the recipient that they had allegedly received a faxed document. Clicking on the attached “document” revealed a request to log in to SharePoint so the user could view the document in the cloud. This login request sent any submitted credentials to the attackers before redirecting the user to a legitimate Microsoft SharePoint page.
It was less than a year later when Cofense came across a phishing email that claimed a third-party vendor wanted the recipient to view a proposal document. When they clicked on the embedded link, the recipient found themselves redirected to a compromised SharePoint account. This account displayed a malicious OneNote document that, when downloaded, redirected the user to a OneDrive imitation site designed to phish their Microsoft credentials.
A few months after that, PhishLabs discovered a phishing example that impersonated an automated SharePoint notification. The attack email prompted the user to open a shared copy of a Q4 2019 report. Clicking on the ‘Open’ button led them to a destination that included login.microsoftonline.com, a legitimate Microsoft domain. This link destination prompted the user to log into their Microsoft account. At that point, the attack prompted the user to approve a series of permission requests for a fake Microsoft app called ‘0365.’ This app gave attackers control of their victim’s account without requiring their username and password.
At the start of 2020, Graphus observed a phishing attack that began with a link to a SharePoint document. The link redirected the user to a page that looked like a Microsoft OneDrive login page. When they clicked the ‘Review Document’ link, the attack redirected them to another page. This, in turn, prompted them to log in using their Microsoft, AOL or other email account. This page sent whatever credentials entered by the user over to the attackers.
How to Defend Against a Phishing Attack
Security professionals can help their organizations defend against a phishing attack by making sure they have a layered approach to email security. This strategy should consist of regularly sending phishing simulations designed to evaluate every employee’s familiarity with email-borne attacks and using ongoing role-based training to familiarize everyone with emerging digital threats. Simultaneously, security personnel should keep track of their organization’s typo-squatted domains and use email security controls to flag messages that come from blacklisted domains, contain disabled attachments and/or originate from outside of the organization.
David Bisson is an infosec news junkie and security journalist. He works as Contributing Editor for Graham Cluley Security News and Associate Editor for Trip...