On January 1, we detected a significant increase in activity from one of the web skimmer groups we’ve been tracking. During this time, we found their malicious skimming code (detected by Trend Micro as JS_OBFUS.C.) loaded on 277 e-commerce websites providing ticketing, touring, and flight booking services as well as self-hosted shopping cart websites from prominent cosmetic, healthcare, and apparel brands. Trend Micro’s machine learning and behavioral detection technologies proactively blocked the malicious code at the time of discovery (detected as Downloader.JS.TRX.XXJSE9EFF010).

The activities are unusual, as the group is known for injecting code into a few compromised e-commerce websites then keeping a low profile during our monitoring. Further research into these activities revealed that the skimming code was not directly injected into e-commerce websites, but to a third-party JavaScript library by Adverline, a French online advertising company, which we immediately contacted.