A risk actor has been abusing hyperlink wrapping providers from reputed expertise corporations to masks malicious hyperlinks resulting in Microsoft 365 phishing pages that acquire login credentials.
The attacker exploited the URL safety function from cybersecurity firm Proofpoint and cloud communications agency Intermedia in campaigns from June via July.
Some electronic mail safety providers embrace a hyperlink wrapping function that rewrites the URLs within the message to a trusted area and passes them via a scanning server designed to dam malicious locations.
Legitimizing phishing URLs
Cloudflare’s Electronic mail Safety crew found that the adversary legitimized the malicious URLs after compromising Proofpoint and Intermedia-protected electronic mail accounts, and certain used their unauthorized entry to distribute the “laundered” hyperlinks.
“Attackers abused Proofpoint hyperlink wrapping in a wide range of methods, together with multi-tiered redirect abuse with URL shorteners by way of compromised accounts,” the researchers stated.
“The Intermedia hyperlink wrapping abuse we noticed additionally centered on gaining unauthorized entry to electronic mail accounts protected by hyperlink wrapping“ – Cloudflare Electronic mail Safety
The risk actor added an obfuscation layer by first shortening the malicious hyperlink earlier than sending it from a protected account, which robotically wrapped the hyperlink.
The researchers say that the attacker lured victims with pretend notifications for voicemail or shared Microsoft Groups paperwork. On the finish of the redirect chain was a Microsoft Workplace 365 phishing web page that collected credentials.
Microsoft 365 phishing delivered by exploiting link-wrapping function
supply: Cloudflare Electronic mail Safety
Within the marketing campaign that abused Intermedia’s service, the risk actor delivered emails pretending to be a “Zix” safe message notification for a viewing a safe doc, or impersonated a communication from Microsoft Groups informing of a newly acquired message.
The hyperlink allegedly resulting in the doc was a URL wrapped by Intermedia’s service and redirected to a pretend web page from digital and electronic mail advertising and marketing platform Fixed Contact internet hosting the phishing web page.
Clicking on the reply button within the pretend Groups notification led to a Microsoft phishing web page that may acquire login credentials.
By disguising the malicious locations with professional electronic mail safety URLs, the risk actor elevated the possibilities of a profitable assault, the Cloudflare researchers stated.
It ought to be famous that abusing professional providers to ship malicious payloads is just not new however exploiting the link-wrapping safety function is a current growth on the phishing scene.
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