In this attack, attackers send emails through SurveyMonkey in order to steal Microsoft credentials of employees.
Quick Summary of Attack Target
Platform: Office 365
Email Security Bypassed: Office 365
Mailboxes in Organization: 15,000 to 50,000
Payload: Malicious Link
Technique: Spear Phishing
What was the attack?
- Setup: SurveyMonkey is a survey service that is normally used to host legitimate surveys. However, sometimes attackers will utilize file sharing and surveying sites like SurveyMonkey to host redirect links to a phishing webpage. By using these legitimate services, attackers can bypass email URL detection systems deployed by many email security tools.
- Email Attack: The email is sent from a real SurveyMonkey domain (surveymonkeyuser.com), but with a different reply-to domain. That reply-to domain was registered only 1 month ago. The email simulates an automated notification with a link to open the “survey”. This link is an actual SurveyMonkey link that redirects to the main phishing page.
- Payload: Within the body of the email is a hidden redirect link appearing as the text “Navigate to access statement” with a brief message “Please do not forward this email as its survey link is unique to you”. But clicking on the link redirects to a site hosted on a Microsoft form submission page. This form asks the user to enter their Office 365 email and password.
- Result: If the user is not vigilant and provides their credentials, the user account would be compromised.
Why is this attack effective?
- Concealed URL: Since the URL isn’t visible within the body text, it is easy to miss at first glance. The first link redirects to a real survey monkey link, and then finally to the landing page of the phishing site.
- Trusted Sender: As these emails originated from the legitimate SurveyMonkey email address, and the body of the email contains a link to the real survey monkey domain, one would easily believe the email to be benign. However, it isn’t until the second redirect where the user is led to a phishing page that the attacker controls.
- Predictable Behavior: Because the email mentions that each survey link is unique to each recipient of the email, users may be primed to think that the login page is there to validate that their responses are from the legitimate recipient of the email. Thus, the behavior isn’t unexpected (even if it’s aytpical – recipients should never enter their email credentials into a survey, regardless of which service is providing it).