Attackers Exploit Public .env Files to Breach Cloud and Social Media Accounts

A large-scale extortion campaign has compromised various organizations by taking advantage of publicly accessible environment variable files (.env) that contain credentials associated with cloud and social media applications.

“Multiple security missteps were present in the course of this campaign, including the following: Exposing environment variables, using long-lived credentials, and absence of least privilege architecture,” Palo Alto Networks Unit 42 said in a Thursday report.

The campaign is notable for setting its attack infrastructure within the infected organizations’ Amazon Web Services (AWS) environments and using them as a launchpad for scanning more than 230 million unique targets for sensitive data.

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With 110,000 domains targeted, the malicious activity is said to have netted over 90,000 unique variables in the .env files, out of which 7,000 belonged to organizations’ cloud services and 1,500 variables are linked to social media accounts.

“The campaign involved attackers successfully ransoming data hosted within cloud storage containers,” Unit 42 said. “The event did not include attackers encrypting the data before ransom, but rather they exfiltrated the data and placed the ransom note in the compromised cloud storage container.”

The most striking aspect of the attacks is that it doesn’t rely on security vulnerabilities or misconfigurations in cloud providers’ services, but rather stems from the accidental exposure of .env files on unsecured web applications to gain initial access.

A successful breach of a cloud environment paves the way for extensive discovery and reconnaissance steps with an aim to broaden their foothold, with the threat actors weaponizing AWS Identity and Access Management (IAM) access keys to create new roles and escalate their privileges.

The new IAM role with administrative permissions is then used to create new AWS Lambda functions to initiate an automated internet-wide scanning operation containing millions of domains and IP addresses.

“The script retrieved a list of potential targets from a publicly accessible third-party S3 bucket exploited by the threat actor,” Unit 42 researchers Margaret Zimmermann, Sean Johnstone, William Gamazo, and Nathaniel Quist said.

“The list of potential targets the malicious lambda function iterated over contained a record of victim domains. For each domain in the list, the code performed a cURL request, targeting any environment variable files exposed at that domain, (i.e., https://<target>/.env).”

Should the target domain host an exposed environment file, the cleartext credentials contained within the file are extracted and stored in a newly created folder within another threat actor-controlled public AWS S3 bucket. The bucket has since been taken down by AWS.

The attack campaign has been found to specifically single out instances where the .env files contain Mailgun credentials, indicating an effort on the part of the adversary to leverage them for sending phishing emails from legitimate domains and bypass security protections.

The infection chain ends with the threat actor exfiltrating and deleting sensitive data from the victim’s S3 bucket, and uploading a ransom note that urges them to contact and pay a ransom to avoid selling the information on the dark web.

The financial motivations of the attack are also evident in the threat actor’s failed attempts to create new Elastic Cloud Compute (EC2) resources for illicit cryptocurrency mining.

It’s currently not clear who is behind the campaign, in part due to the use of VPNs and the TOR network to conceal their true origin, although Unit 42 said it detected two IP addresses that were geolocated in Ukraine and Morocco as part of the lambda function and S3 exfiltration activities, respectively.

“The attackers behind this campaign likely leveraged extensive automation techniques to operate successfully and rapidly,” the researchers said. “This indicates that these threat actor groups are both skilled and knowledgeable in advanced cloud architectural processes and techniques.”

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