A new attack campaign has compromised more than 3,500 websites worldwide with JavaScript cryptocurrency miners, marking the return of browser-based cryptojacking attacks once popularized by the likes of CoinHive. Although the service has since shuttered after browser makers took steps to ban miner-related apps and add-ons, researchers from the c/side said they found evidence of a stealthy miner packed within obfuscated JavaScript that assesses the computational power of a device and spawns background Web Workers to execute mining tasks in parallel without raising any alarm. More importantly, the activity has been found to leverage WebSockets to fetch mining tasks from an external server, so as to dynamically adjust the mining intensity based on the device capabilities and accordingly throttle resource consumption to maintain stealth. "This was a stealth miner, designed to avoid detection by staying below the radar of both users and security tools," security researcher Himanshu Anand said. The net result of this approach is that users would unknowingly mine cryptocurrency while browsing the compromised website, turning their computers into covert crypto generation machines without their knowledge or consent. Exactly how the websites are breached to facilitate in-browser mining is currently not known. Further dissection has determined that over 3,500 websites have been ensnared in the sprawling illicit crypto mining effort, with the domain hosting the JavaScript miner also…Read More