Hackers Using Google Cloud Computing Platform To Deliver Targeted Malware Attacks via Weaponized PDF

Threat actors use the Google computing platform (GCP) to deliver the malware through malicious PDF files. The attack targeted governments and financial firms worldwide.

According to Netskope Threat Research Labs detected the target based on its 42 customer instances and likely the attacks to be launched by the infamous hacking group Cobalt Strike.

Last year Cybercriminals abused legitimate Google Cloud Storage services to host malicious payloads and delivered to compromise the organization’s networks by bypassing the security controls.

In this campaign, attackers used traditional email Crafted in a way to appear like a legitimate one and carry the malicious PDF document as an attachment in the mail.

The PDF’s found to be created with Adobe Acrobat and they contain HTTPS URLs in a compressed form and all the decoys used in delivering the payload.

“The targeted attack is more convincing than the traditional attacks and these attacks are carried out by abusing the GCP URL redirection in PDF decoys and redirecting to the malicious URL hosting the malicious payload.”

Attackers abused the GoogleApp Engine URL and redirect the victim to download the malware-hosted sites, which makes the victims to believe that they are downloading from a trusted source.

URL Redirection – Google Cloud Computing

According ot Netskope illustration on the decoy URL is accessed by the user, it logs out from appengine.google.com and generates a 302 status code of redirection.

once this action is triggered it redirects the user to google.com/logout?continue=, by using those redirection logic threat actors make the victims reach the destination landing page and download Doc102018[.]doc to the victim machine.

Even though it is an unvalidated redirect GCP App Engine application successfully validated all the redirection and delivers the payload to the victim’s machine.

Threat actors abused the Unvalidated Redirects and Forwards vulnerability with GCP App Engine and redirect victims to download to a malicious appended URL hosting the malicious payload, reads Netscape report.

The word document Doc102018.doc downloaded from https://transef[.]biz contains macros that download the second stage of the payloads from https://transef[.]biz/fr.txt.

Downloaded txt document “fr[.]txt” exploits use native Windows application Microsoft Connection Manager Profile Installer to download and execute the payload, researchers call it a Squiblydoo technique.

“Based on our threat intelligence research, more than 20 other banking, government, and financial institutions were targeted with the same attack via phishing emails sent by the attackers posing as legitimate customers of those institutions say Netscape.”

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