The dirty dozen of Latin America: From Amavaldo to Zumanek

Besides Amavaldo, which became dormant, all the other families remain active to this day.
Brazil is still the most targeted country, followed by Spain and Mexico.
Grandoreiro and Mekotio expanded to Europe – mainly Spain.
What started as several minor campaigns, likely to test the new territory, evolved into something much grander.
Latin American banking trojans used to change rapidly.
In the early days of tracking, some of them were adding to or modifying their core features several times a month.
Nowadays they still change very often, but the core seems to remain mostly untouched.
Due to the partially stabilized development, researchers believe the operators are now focusing on improving distribution.

The campaigns researchers see always come in waves and more than 90% of them are distributed through spam.
One campaign usually lasts for a week at most. Previously, researchers have seen Grandoreiro, Ousaban and Casbaneiro increasing their reach enormously compared to their previous activity,
Latin American banking trojans require a lot of conditions to attack successfully:

– Potential victims need to follow steps required to install the malware on their machines
– Victims need to visit a targeted website and log into their accounts
– Operators need to react to this situation and manually command the malware to display the fake pop-up window and take control of the victim’s machine
– Victims need to not suspect malicious activity and possibly even enter an authentication code in the case of 2FA

This malware family was active in Brazil.
Its most noticeable characteristic was its usage of well-known cryptographic methods to encrypt strings, as opposed to the majority of Latin American banking trojans that mainly use custom encryption schemes, some of which are shared across these families.
Researchers have observed Krachulka variants using AES, RC2, RC4, 3DES and a slightly customized variant of Salsa20.

Krachulka, despite being written in Delphi like most other Latin American banking trojans, was distributed by a downloader written in the Go programming language – another unique characteristic among this kind of banking malware.

Researchers were able to identify additional builds, each dedicated to target a different country – Brazil, Chile and Colombia.
The most identifying feature of Lokorrito is its usage of a custom User-Agent string in network communication.
Researchers have observed two values – LA CONCHA DE TU MADRE and 4RR0B4R 4 X0T4 D4 TU4 M4E, both quite vulgar expressions in Spanish and Portuguese, respectively.
Researchers have identified several additional Lokorrito-related modules.
First, a backdoor, which basically functions like a simplified version of the banking trojan without the support for fake overlay windows.
Researchers believe it was installed in some Lokorrito campaigns first and, only if the attacker saw fit, it was updated to the actual banking trojan.
Then, a spam tool, which generates spam emails distributing Lokorrito and sending them to further potential victims.
The tool generated the emails based on both hardcoded data and data obtained from a C&C server.
Finally, researchers identified a simple infostealer designed to steal the victim’s Outlook address book and a password stealer intended to harvest Outlook and FileZilla credentials.

This malware family was active exclusively in Brazil.
It was the first Latin American banking trojan malware family ESET identified.

Zumanek is identified by its method for obfuscating strings.
It creates a function for each character of the alphabet and then concatenates the result of calling the correct functions in sequence.

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