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Threat actors are leveraging top tier cloud apps to host phishing baits. Netskope Threat Labs has identified an ongoing O365 phishing campaign hosted in Google App Engine with the credential harvester mostly hosted in Azure App Service. This phishing campaign typically targets O365 users via phishing emails with a direct link or attachment.
The campaign started in late June 2020 and is still active today. Based on similarities in the phishing pages, we believe the same threat actor is responsible for generating more than 100 phishing pages and continues to add more daily. These phishing pages and attack elements were hosted in different App Engine and Azure websites. At the time of writing, more than 60% of the URLs we observed were active and not detected or blocked by security scanning services in popular browsers like Chrome and Firefox.
Our earlier posts Phishing in the public cloud: You’ve been served and Amazon themed Phish hosted in Azure Sites detailed phishing attacks that used Azure Websites to serve up parts of the attack. This ongoing campaign indicates that threat actors are continuing to use cloud services to launch phishing attacks at scale from widely used cloud services, making it harder for users to recognize and vendors to detect, block, or take down.
This blog post details our analysis of this campaign and provides recommendations to help protect you and your organization from falling victim to similar phishing campaigns.
Appspot.com – Phishing baits
Google App Engine is a Google Cloud Platform (GCP) service for developing and hosting web applications. App Engine allows you to serve SSL (HTTPS) traffic through your appspot.com domain, https://<app>.r.appspot.com. Users tend to place trust in websites that are hosted by top-tier vendors like Google. Threat actors are exploiting this trust by hosting phishing baits in Google services as shown in Figure 1.
Analysis of the phishing campaign
The attack starts with a bitly link shortener link, https://bitly[.]com/33nMLkZ, generally distributed via phishing emails that redirect to https://o365apps[.]oa.r.appspot.com as shown in Figure 2.