HUMAN‘s Satori Threat Intelligence team has uncovered a cluster of VPN apps on the Google Play Store that covertly transform Android devices into residential proxies (RESIPs) for malicious purposes. Codenamed PROXYLIB, these apps utilize a Golang library to establish a network of proxies without user consent, allowing threat actors to obfuscate their origins and conduct various attacks. Google has since removed the 29 identified apps, highlighting the abuse of residential proxies by cybercriminals.
Residential proxies, sourced from real IP addresses provided by ISPs, offer anonymity benefits but are susceptible to exploitation by threat actors for nefarious activities. By routing internet traffic through intermediary servers, these proxies help attackers mask their true IP addresses and conduct attacks from different residential locations. Malware operators can exploit unsuspecting users by tricking them into installing bogus apps that corral devices into a botnet, monetizing access to the network.
The Android VPN apps discovered by HUMAN are designed to enroll infected devices into the proxy network by establishing contact with a remote server and processing requests from the network. Additionally, a subset of these apps incorporates a software development kit (SDK) from LumiApps, facilitating the bundling of proxyware functionality. LumiApps’ SDK service allows users to upload legitimate APK files, which are then bundled with the proxyware and distributed through various channels, including the Google Play Store.
Evidence suggests that the threat actor behind PROXYLIB is selling access to the proxy network created by the infected devices through companies like LumiApps and Asocks. Moreover, LumiApps incentivizes developers to embed its SDK into their apps by offering cash rewards based on the amount of traffic routed through user devices. The misuse of residential proxies underscores the fragmented yet interconnected ecosystem of proxyware services, emphasizing the need for greater transparency and user awareness to mitigate the risks associated with such malicious activities.
