Pervasive Brazilian financial malware targets bank customers in Latin America and Europe

UAC_2

Research by: Assaf Dahan and Joakim Kandefelt

Executive Summary

For more than a decade, Brazil has been considered a major contributor to global cybercrime. Countless security reports have detailed a plethora of nefarious activities linked to Brazilian threat actors, who mainly target the financial and private sector. Brazil is particularly known for being home to huge botnets that send out spam and phishing emails and proliferate infostealers and banking Trojans. After India and China, Brazil is the world's third worst botnet infected country, according to The Spamhaus Project.

In 2018, Cybereason’s Nocturnus team analyzed numerous campaigns related to several Brazilian financial malware. This blog shows the pervasiveness of these Brazilian-made malware, which target online banking customers of over 60 banks in nearly a dozen countries throughout Latin America, Spain and Portugal. This blog continues research presented in our earlier blog and maps the evasive infection and delivery methods used by Brazilian threat actors in order to distribute malware.

MAPPING RECENT BRAZILIAN FINANCIAL MALWARE DELIVERY METHODS

The campaigns, which target customers of more than 60 banks worldwide, deliver different kinds of financial malware. Antivirus vendors have assigned this type of malware generic names like: Banload, Banbra, Bancos, Boleto, Delf and Spy.Banker. Despite the variation in the final malware payload, Cybereason identified three key stages that were common to most of the attacks involving Brazilian financial malware.

The multi-stage delivery infrastructure helps attackers to minimize the risk of detection. By implementing various evasive techniques, the attackers successfully bypass signature/heuristic-based engines, thus ensuring the delivery of the final malware. While the multi-stage delivery approach is not new in cybercrime, its adoption by Brazilian threat actors has proven to be highly effective at evading many anti-virus products, as demonstrated by the low detection rate presented in our research.

In each stage, we observed commonalities in the tools, techniques and procedures (TTPs) that are shared across campaigns. These TTPs include:

  • Social engineering as an entry point
  • Multiple redirections via URL shorteners and the usage of Dynamic DNS services
  • Payloads hosted on legitimate online storage services and CDNs (content delivery networks)
  • Obfuscated PowerShell downloaders employing command-line logging evasion
  • Living off the land techniques that abuse Microsoft-signed binaries
  • Abusing trusted applications via DLL hijacking
  • Splitting the main payload into two or more components

Related Post-infection Malware

Our research revealed interesting aspects of the Brazilian malware ecosystem. We observed different types of Brazilian malware being used in conjunction by the same threat actor. In some of the endpoints infected with Brazilian financial malware, we noticed additional Brazilian-made malware, such as infostealers, cryptocurrency miners and a malware that steals data from Microsoft Outlook. This finding gives us a glimpse into the different ways in which threat actors can capitalize on previously gained foothold, in order to increase their potential profits. 

Brazilian-made Malware, Spanish-Speaking Targets

Discussing Brazilian financial malware may imply that this threat only targets Brazilian online banking customers, but our research clearly shows that Brazilian threat actors have expanded their operation to Spanish-speaking countries in Latin America and Spain.

Observed targeted countries: Brazil, Argentina, Chile, Bolivia, Colombia, México, Venezuela, Portugal and Spain

Based on the data from recent campaigns, Spain is the most second targeted country after Brazil. Other countries targeted in recent campaigns include Mexico, Argentina, Venezuela, Colombia, Bolivia and Chile.

Our research demonstrates how different types of Brazilian-made malware, originally designed to target Brazilian banking users, were repurposed to target other countries and their respective regional banks. We observed references to more than 60 banks embedded within the malware's code. (See the list of targeted banks in this section).

URLs of foreign banks embedded in a Brazilian malware

One Source-code, Many variants

Cybereason analysts were able to trace the origin of various Brazilian malware to a Remote Access Tool (RAT), whose source code is publicly available on Github. While the identity of the author is known, there is no proof that this author has a direct link to the financial malware discussed in this blog. Cybereason estimates that the publicly-available source code was repurposed by different threat actors who later added banking modules as well as anti-analysis features, that were present in the financial malware analyzed in this blog.

Article Link: https://www.cybereason.com/blog/brazilian-financial-malware-banking-europe-south-america