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A new phishing campaign can bypass multi-factor authentication (MFA) on Office 365 to access victims’ data stored on the cloud and use it to extort a Bitcoin ransom or even find new victims to target, security researchers have found.

Researchers at Cofense Phishing Defense Center discovered the tactic, which leverages the OAuth2 framework and OpenID Connect (OIDC) protocol and uses a malicious SharePoint link to trick users into granting permissions to a rogue application, researcher Elmer Hernandez wrote in a blog post published Tuesday.

The attack is different than a typical credential harvester in that it attempts to trick users into granting permissions to the application, which can bypass MFA, he said. MFA is used as back-up security to a user’s password in case the password is compromised and is meant to protect an account in such a scenario.

“This is not the first time the tactic has been observed, but it’s a stark reminder that phishing isn’t going to be solved by multi-factor authentication,” Hernandez noted.

If attackers are successful, they can engage in a number of threat behaviors, researchers said. The most basic attack can steal all the victims’ email and access cloud hosted documents containing sensitive or confidential information. But attackers wouldn’t have to stop there, he said.

“Once the attacker has sensitive information, they can use it to extort victims for a Bitcoin ransom,” Hernandez wrote. “The same permissions can also be used to download the user’s contact list to be used against fresh victims. Using the address book and old emails would allow the attacker to create hyper-realistic Reply-Chain phishing emails.”
Full report by Cofense:
 
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