Threat Actors Obfuscate JavaScript to Hide Crypto-Mining Malware

Security researchers recently observed threat actors burying crypto-mining malware inside compromised websites to hijack victims’ computing resources.

Victims who visited a site infected with the malicious JavaScript code unwittingly unleashed a payload that was hidden within a header file of a WordPress theme, according to researchers from Sucuri.

Although the file itself was legitimate, the code obfuscated the crypto-mining malware and kept it at bay until it confirmed that:

  • The malware wouldn’t be detected via automated scans; and
  • The victim’s device had the central processing unit (CPU) power necessary to mine cryptocurrencies such as bitcoin and Monero.

After the malware confirmed that the infected device met these criteria, it began the mining process.

What Is Crypto-Mining Malware?

Cybercriminals have been using banking Trojans and other tools to mine cryptocurrency since at least 2013, according to the “IBM X-Force Threat Intelligence Index 2018.” One of the most common methods to date has involved mobile apps and websites laden with malicious code hidden inside ads, otherwise known as malvertising.

Coin-stealing has traditionally involved very basic pieces of malware that work over time on a victim’s endpoint. In this recent case, however, researchers were only able to discover the crypto-mining malware after refactoring the code and examining it in detail. Meanwhile, such attacks can drain smartphones, desktops and other systems to enrich the attackers.

How to Keep Crypto-Miners Away From Your Devices

To protect enterprise networks from crypto-mining malware, security experts recommend creating an inventory of all applications in use across the enterprise, then categorizing them by risk attributes, such as whether they are internal or customer-facing.

Security teams should also evaluate applications based on criticality, impact, reputational damage and loss of personally identifiable information (PII), for example. As this incident suggests, however, the impact of a crypto-mining attack could also include loss of computing resources to stealthy cryptocurrency miners.

Source: Sucuri

Shane Schick

Writer & Editor

Shane Schick is a writer, editor and speaker who focuses on how information technology creates business value. He lives...