A new phishing campaign leveraged DocuSign branding along with a landing page hosted on Amazon public cloud storage (S3) to target users’ Microsoft Office credentials.

In late July, Proofpoint researchers observed a phishing campaign that used branding from electronic signature service DocuSign to target a small number of individuals in organizations across multiple verticals. Emails directed recipients to a landing page that also contained DocuSign branding on Amazon S3, a phishing site designed to steal users’ Office 365 credentials.

The attackers used extensive XOR obfuscation to safeguard their phishing landing page. Further investigation revealed that the threat actor behind this campaign had hosted other low-volume campaigns on AWS domains. Many of these similarly abused DocuSign and targeted users’ Microsoft Office credentials, but some of those attacks also exploited ShareFile.

A Rise in Cloud-Hosted Phishing Attacks

Cybercriminals have often turned to the cloud to host their phishing landing pages in the past several months. In February, for instance, EdgeWave observed attackers abusing Microsoft Azure to host a landing page for a campaign designed to steal employees’ Facebook credentials.

Netskope detected a similar operation targeting users’ Amazon details just a few months later. Similarly, the Zscaler ThreatLabZ team detected a phishing campaign that leveraged both Microsoft Azure and Microsoft SSL certificates to harvest unsuspecting users’ Outlook credentials.

How Quickly Can You Detect a Phishing Campaign?

Security leaders should consider investing in machine learning solutions to improve the speed at which their defenses can spot and block phishing domains. Analyzing phishing data in machine-deliverable threat intelligence can also help security teams prioritize specific attacks based on their threat rankings.