ESET Research continues its series on Latin American banking trojans, this time dissecting Numando, which targets mainly Brazil and rarely Mexico and Spain. Numando is similar to the other malware families described in this series in its use of fake overlay windows, backdoor functionality, and abuse of public services such as YouTube to store its remote configuration. However, unlike most of the other Latin American banking trojans, Numando does not show signs of continuous development.
The threat actor behind this malware family has been active since at least 2018. “Even though Numando is not nearly as lively as other trojans such as Mekotio or Grandoreiro, it has been consistently used since we started tracking it, bringing interesting new techniques to the pool of Latin American banking trojans’ tricks,” says Jakub Souček, coordinator of the ESET team that analyzed Numando.
Numando’s backdoor capabilities allow it to simulate mouse and keyboard actions, restart and shut down the machine, display overlay windows, take screenshots, and kill browser processes. It utilizes fake overlay windows to lure sensitive information out of its victims.
Among the new techniques, Numando uses seemingly useless ZIP archives or bundles payloads with decoy BMP images that are suspiciously large. These BMP files are valid images that can be opened in a majority of image viewers and editors without issue. Numando is distributed almost exclusively by spam.
Like many other Latin American banking trojans, Numando abuses public services to store its remote configuration – YouTube and Pastebin – in this case. Google took the YouTube videos down promptly based on ESET’s notification.