Gmail’s multi-factor authentication bypassed by hackers to pull off targeted attacks

Russian hackers have bypassed Google’s multi-factor authentication (MFA) in Gmail to pull off targeted attacks, according to security researchers at Google Threat Intelligence Group (GTIG).

The hackers pulled this off by posing as US Department of State officials in advanced social engineering attacks, building a rapport with the target and then persuading them into creating app-specific passwords (app passwords).

App passwords are special 16-digit codes that Google generates to allow certain apps or devices to access your Google Account securely, especially when you have MFA enabled.

Normally, when you sign in to your Google account, you use your regular password plus a second verification step like a code sent to your phone. But since some older or less secure apps and devices—like certain email clients, cameras, or older phones—are unable to handle this extra verification step, Google provides app passwords as an alternative way to sign in.

However, because app passwords skip the second verification step, hackers can steal or phish them more easily than a full MFA login.

In an example provided by CitizenLab, the attackers initially made contact by posing as a State Department representative, inviting the target to a consultation in the setting of a private online conversation.

Although the invitation came from a Gmail account, it CCed four @state.gov accounts, giving a false sense of security and making the target believe that other people at the State Department had monitored the email conversation.

Most likely, the attacker fabricated those email addresses, knowing that the State Department’s email server accepts all messages and does not send a bounce response even if the addresses do not exist.

As the conversation unfolded and the target showed interest, they received an official looking document with instructions to register for an “MS DoS Guest Tenant” account. The document outlined the process of  “adding your work account… to our MS DoS Guest Tenant platform,” which included creating an app password to “enable secure communications between internal employees and external partners.”

So, while the target believes they are creating and sharing an app password to access a State Department platform in a secure way, they are actually giving the attacker full access to their Google account.

The targets of this campaign, which ran for months, were prominent academics and critics of Russia, and was set up with so much attention for details and skill that the researchers suspect the attacker was a Russian state-sponsored entity.

Be safe, avoid app passwords

Now that this bypass is known, we can expect more social engineering attacks leveraging app-specific passwords in the future. Here’s how to stay safe:

• Only use app passwords when absolutely necessary. If you have the opportunity to change to apps and devices that support more secure sign-in methods, make that switch.
• The advice to enable MFA still stands strong, but not all MFA is created equal. Authenticator apps (like Google Authenticator) or hardware security keys (FIDO2/WebAuthn) are more resistant to attacks than SMS-based codes, let alone app passwords.
• Regularly educate yourself and others about recognizing phishing attempts. Attackers often bypass MFA by tricking users into revealing credentials or app passwords through phishing.
• Keep an eye on unusual login attempts or suspicious behavior, such as logins from unfamiliar locations or devices. And limit those logins where possible.
• Regularly update your operating system and the apps you use to patch vulnerabilities that attackers might exploit. Enable automatic updates whenever possible so you don’t have to remember yourself.
• Use security software that can block malicious domains and recognize scams.

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