Research

Brazil: new crypto challenge

Some time ago I wrote an article about how Brazilian banker Trojans work but time is running out and Brazilian coders are trying to improve their skills, making more complex methods of infection. The proof of this is the sample I worked on today. The infection scheme is the classic one:

A scam message with links to fake pictures —-> Downloading and
executing of the initial Trojan.Downloader —-> Downloading and
installation of Trojan.Bankers

A new (for Brazil) concept takes place between second and third stages when the Trojan.Downloader downloads and installs the Banker. On the one hand Brazilian coders obfuscate the download links using several techniques and on the other hand now they also crypt the Banker to be downloaded to the system.

For example, if you deobfuscate the malicious links and try to download the Trojans behind them you will see something like this:

It’s a crypted (specially packed) PE file. The coders from Brazil use this technique to prevent an automated malware analysis and monitoring mode by AV companies. This sample downloaded as it is on the server won’t be functional on the user machine unless
it’s decrypted. The decryption mechanism in this case is included into the initial Trojan.Downloader, which first downloads malware, and then decrypts it to be able to infect the user machine:

Now spot the difference: It’s the same file but after decryption looks like a standard malicious PE file and can be used to infect the victim:

This particular sample is detected by Kaspersky Anti-Virus as Trojan-Banker.Win32.Banker.aumz and it attacks customers of the 3 most largest banks of Brazil.

Brazil: new crypto challenge

Your email address will not be published. Required fields are marked *

 

Reports

APT trends report Q3 2021

The APT trends reports are based on our threat intelligence research and provide a representative snapshot of what we have discussed in greater detail in our private APT reports. This is our latest installment, focusing on activities that we observed during Q3 2021.

Lyceum group reborn

According to older public researches, Lyceum conducted operations against organizations in the energy and telecommunications sectors across the Middle East. In 2021, we have been able to identify a new cluster of the group’s activity, focused on two entities in Tunisia.

GhostEmperor: From ProxyLogon to kernel mode

While investigating a recent rise of attacks against Exchange servers, we noticed a recurring cluster of activity that appeared in several distinct compromised networks. With a long-standing operation, high profile victims, advanced toolset and no affinity to a known threat actor, we decided to dub the cluster GhostEmperor.

Subscribe to our weekly e-mails

The hottest research right in your inbox