Hiding in Plain Sight: An Empirical Study of Web Application Abuse in Malware

Web applications provide a wide array of utilities that are abused by malware as a replacement for traditional attacker-controlled servers. Thwarting these Web App-Engaged (WAE) malware requires rapid collaboration between incident responders and web app providers. Unfortunately, our research found that delays in this collaboration allow WAE malware to thrive. We developed Marsea, an automated malware analysis pipeline that studies WAE malware and enables rapid remediation. Given 10K malware samples, Marsea revealed 893 WAE malware in 97 families abusing 29 web apps. Our research uncovered a 226% increase in the number of WAE malware since 2020 and that malware authors are beginning to reduce their reliance on attacker-controlled servers. In fact, we found a 13.7% decrease in WAE malware relying on attacker-controlled servers. To date, we have used Marsea to collaborate with the web app providers to take down 50% of the malicious web app content.