Microsoft States Phishing Bypassed MFA for Email Access

Microsoft recently revealed online miscreants aggressively targeted 10,000+ organizations dating back to last fall. The tech giant is warning its business email clients about a massive phishing campaign designed to avoid multifactor authentication, obtain access to inboxes and engage in fraudulent activity.

How is the Phishing Campaign Conducted?

The digital evildoers commit fraud by accessing corporate vendors' payment data. Several campaign variations have compromised thousands of businesses in less than ten months. The campaign centers on business email compromise in which aggressors transmit requests to obtain information or money from what seems to be a legitimate party. Also referred to as vendor compromise, this Cxo Fraud technique has proven quite successful.

How can Companies Defend Against the Attack?

Digital security specialists are pushing businesses to implement multifactor authentication to sidestep online threats. MFA implements login security layers by mandating that users provide a password along with another piece of evidence to prove legitimacy. For example, a one-time password can be transmitted to a hardware token or a properly registered device.

How are Hackers Bypassing MFA?

Threat actors have found creative workarounds to MFA. The threat actors established a proxy server connected through links transmitted by way of a phishing message. The proxy server obtains the username and password along with the web session cookies by serving as an intermediary between the company's email clients who accessed the links and the company's actual portal to access email. Most call this strategy a man-in-the-middle technique. The method is effective as only those who carefully analyzed the phony login page would be aware that it is an attempt to fool wayward web users into falling into a trap.

The proxy server even prevents a replica of the Microsoft login page for email access. The only nuanced difference between the two is the URL. However, the average computer user is unlikely to notice that the URL is slightly different. Once the session cookie is acquired, hackers can inject it into the web browser to bypass the authentication, regardless of whether the MFA has been enabled.

The hackers also implemented an open-source toolkit called the Evilginx2 phishing kit. This toolkit functions as the man in the middle component of the scam. The digital miscreants transmitted the phishing message to make it known that the intended recipients received a voicemail. The email message with the HTML file was attached, triggering a loading into the target's web browser upon opening. The following page made it clear that the voice message was available for download.

The user is then redirected to the hackers' site while the download bar representing progress was implemented within the HTML file. That series ensures that redirection could complete the phony login page with the users' information. The next step is even more analysis to determine if the login request originated from the email address of the targeted user that was originally embedded within the URL of the proxy.

How Quick is the Attack?

The hackers behind this offensive required merely five minutes after the session and credential theft to attempt payment fraud. Transmitting replies to email threads tied to the invoices and payments set the stage for obtaining payment information.

Is Multifactor Authentication Pointless?

Microsoft insists multifactor authentication is not useless. Phishing attacks can potentially compromise multifactor authentication's barrier, yet that barrier is still reasonably effective at thwarting a litany of online threats. Businesses should continuously update their digital security protocols and protections, beware of shady attempts to log in, and possibly consider mandating email logins occur from trusted IP addresses or properly registered computing devices.