Flaw could have granted criminals control over Ever Surf crypto wallets

Check Point uncovers web vulnerability that could have led to cryptocurrency theft

A flaw detected in the browser version of the Ever Surf cryptocurrency wallet could have given hackers who exploited it full control over a targeted user's wallet, say threat hunters at Check Point Research.

The security vulnerability made it possible for threat actors to decrypt the private keys and seed phrases found in the browser's local storage, opening the door to cracking the victim's wallet and accessing the cryptocurrency stored there, the researchers wrote in a blog post Monday.

"As the browser's local storage is unprotected, the data stored there must be securely encrypted," they wrote. "Despite the fact that Surf uses reliable cryptographic libraries for the key derivation and the encryption, the sensitive data in the web version of Surf doesn't appear to have adequate protection."

They were able to run scenarios that revealed that "the combination of the issues found presents several attack vectors that can lead to an attacker obtaining private keys and seed phrases in clear text, which can then be used to gain full control over the victim's wallet."

Check Point's research puts another spotlight on the growing security issues arising in the still-nascent but fast-growing field of blockchain and cryptocurrencies.

Ever Surf plays a number of roles for Everscale (formerly Free TON) blockchain. It not only is a crypto wallet, but it also serves as a messenger service to enable users to chat, a way to send and receive non-fungible tokens (NFTs) and as a blockchain browser.

In addition, it can run Everscale decentralized applications (dApps), which don't need to communicate with a centralized infrastructure like a web server and can interact directly with the blockchain or via a browser extension, such as Metamask.

According to Everscale, it has almost 670,000 accounts and has processed 31.9 million transactions.

There are mobile app versions of Ever Surf that are available in both the Google Play Market and Apple Store sites as well as a web version that runs on any platform. It's in the web version that the vulnerability was found.

In Ever Surf, the keys required to sign transactions are only stored on the user's device and operations involving the blockchain are performed only on the client's side. Because of this, it doesn't have a registration that requires login names and passwords.

When individuals run the application for the first time, they're encouraged to create a new wallet and Ever Surf generates a seed phrase and both public and private keys. At the same time, the user is told to create a six-digit PIN code to log into the app and to confirm transactions.

The keys and seed phrase are stored in the web browser's local storage, which is not protected.

"This means that a human with physical access to the computer or any application or malware such as an infostealer can obtain this data," the threat hunters wrote. "In addition, [local storage] can be accessed by a browser extension, which can then leak the stored data. … Therefore, the browser's local storage cannot be considered secure enough."

Do you register?

Websites that require registration typically don't rely on data stored in cookies or local storage, but also may check the web browser and the user's IP address. They also may require additional user verification. However, with Ever Surf, the data used to control the user's wallet is stored on the computer, so the only protection is strong encryption.

In running its analysis, Check Point was able to show that information-stealing malware could collect large numbers of encrypted keys and seed phrases and brute-force techniques could be used to decrypt the information. From there, attackers would gain control of the wallet. The researchers were able to grab the keystore from a browser's local storage and decrypted the information in 38 minutes.

The digital asset space is rapidly becoming an attractive one to threat groups, which sees a space where the security is still trying to catch up to the innovation and demand is skyrocketing among users who are not tremendously technical. For example, US government agencies last week issued an alert about the notorious Lazarus cybercrime group expanding its focus to include the cryptocurrency and blockchain field.

"Overall, the crypto space can be seen as a whirlwind of opportunities that exist on a largely unregulated environment; this can leave enthusiastic yet naïve consumers at risk from malicious activity," Chris Morgan, senior cyberthreat intelligence analyst at cybersecurity vendor Digital Shadows, told The Register.

"With big money being made amongst crypto investors – but often being stored on insecure locations – threat actors will naturally navigate their activities towards targeting such environments."

The Check Point researchers warned users not to click on suspicious links – particularly those sent by strangers; to keep their operating systems and antivirus software updated; and not to download software and browser extensions from unverified sources. ®

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