In August 2023, security researcher Randy McEoin blogged about a scam he dubbed ClearFake, which uses hacked WordPress sites to serve visitors with a page that claims you need to update your browser before you can view the content.
The fake browser alerts are specific to the browser you’re using, so if you’re surfing the Web with Chrome, for example, you’ll get a Chrome update prompt. Those who are fooled into clicking the update button will have a malicious file dropped on their system that tries to install an information stealing trojan.
Earlier this month, researchers at the Tel Aviv-based security firm Guardio said they tracked an updated version of the ClearFake scam that included an important evolution. Previously, the group had stored its malicious update files on Cloudflare, Guardio said.
But when Cloudflare blocked those accounts the attackers began storing their malicious files as cryptocurrency transactions in the Binance Smart Chain (BSC), a technology designed to run decentralized apps and “smart contracts,” or coded agreements that execute actions automatically when certain conditions are met.
Nati Tal, head of security at Guardio Labs, the research unit at Guardio, said the malicious scripts stitched into hacked WordPress sites will create a new smart contract on the BSC Blockchain, starting with a unique, attacker-controlled blockchain address and a set of instructions that defines the contract’s functions and structure. When that contract is queried by a compromised website, it will return an obfuscated and malicious payload.
“These contracts offer innovative ways to build applications and processes,” Tal wrote along with his Guardio colleague Oleg Zaytsev. “Due to the publicly accessible and unchangeable nature of the blockchain, code can be hosted ‘on-chain’ without the ability for a takedown.”