Guest Blog: Malicious Scripts Gaining Prevalence in Brazil

Posted by    on   Jul 28, 2016

In the run up to VB2016, we invited the conference sponsors to write guest posts for our blog. In the second of this series, ESET's Matías Porolli writes about malicious Visual Basic and JavaScript gaining prevalence in Brazil.

Had we looked at the map of malware detections in Brazil a year ago, we would have seen that the two main computer threats were the downloaders that installed banking trojans, and the banking trojans themselves. Today, the situation remains the same, but with a special extra ingredient – while threats used to predominantly be Windows .exe files, today there are also Java .jar files, as well as Visual Basic Script and JavaScript among the Top 10 threats.

To understand this change in the platforms used by cybercriminals, we analysed both a JavaScript and a Java threat. But first, let's take a look at the Top 10 threat detections in Brazil for the first five months of 2016. The most prevalent is a generic detection of obfuscated scripts; even though the final payload may vary, below we will see a connection between this kind of detection and banking trojans. Although we will not elaborate on the other nine threats, it is worth noting the many different programming languages and platforms that are being used in attacks targeting Brazil today.

Name of the threat Level of prevalence
VBS/Obfuscated.G 10.52%
JS/Danger.ScriptAttachment 4.60%
VBS/Kryptik.FN 3.50%
Win32/Toptools.A 3.09%
JS/TrojanDownloader.Iframe.NKE 2.66%
Java/TrojanDownloader.Banload.AK 2.24%
Java/TrojanDownloader.Banload.AE 2.18%
Win32/Toptools.D 2.18%
JS/Adware.Agent.L 2.09%
JS/Toolbar.Crossrider.G 2.06%

 

In particular, at ESET's Research Lab we have seen a malware campaign in which the threats are being hosted on the MEO cloud service, which is based in Portugal; in most cases, these are banking trojans. The propagation method is via emails with a link to download the malware.

We can take one of those files as an example: Boleto_NFe_1405201421.PDF.js, detected by ESET as VBS/Obfuscated.G.

Although the script code is obfuscated, the encryption used is easy to reverse. Even without decrypting, we can see that a file disguised as a .jpg file is downloaded to the ProgramData folder under the name flashplayer.exe, and is then executed.

Eset-blog-Fig1.png

This file – flashplayer.exe – is in turn a banking trojan downloader, which downloads and runs a third executable named Edge.exe. This executable is detected as a Win32/Spy.KeyLogger.NDW variant; however, apart from recording the keystroke events, it has all the functionalities of a banker. Among its many features, it obtains the address of the website the user is visiting and checks it against a list of banking websites, using DDE, as we described in the article 'Cómo reconstruir lo que envía un troyano desde un sistema infectado' (How to Rebuild What a Trojan Sends From an Infected System).

The difference is that, this time, the trojan includes code for a larger number of browsers including:

Eset-blog-Fig2.png

The strings are encrypted with a custom XOR-based algorithm; some of them can be seen below. It is clearly trying to steal access credentials for Brazilian banking sites.

Eset-blog-Fig3.png

We can see how cybercrime is evolving in Brazil, migrating to new platforms and using various programming languages in its attempt to evade detection. Its goals, however, have not changed that much – stealing banking credentials is still the most profitable attack and is therefore the most common.

For more details on this campaign, visit Matías' full article at WeLiveSecurity.com. More articles from the ESET experts can be found on the latest research section of their blog.

twitter.png
fb.png
linkedin.png
googleplus.png
reddit.png

 

Latest posts:

VB2018 preview: Unpacking the packed unpacker: reversing an Android anti-analysis library

At VB2018, Google researcher Maddie Stone will present an analysis of the multi-layered 'WeddingCake' anti-analysis library used by many Android malware families.

VB2018 preview: From drive-by download to drive-by mining

At VB2018, Malwarebytes researcher Jérôme Segura will discuss the rise of drive-by cryptocurrency mining, explaining how it works and putting it in the broader context of changes in the cybercrime landscape.

Red Eyes threat group targets North Korean defectors

A research paper by AhnLab researcher Minseok Cha looks at the activities of the Red Eyes threat group (also known as Group 123 and APT 37), whose targets include North Korean defectors, as well as journalists and human rights defenders focused on…

VB announces Threat Intelligence Summit to take place during VB2018

We are very excited to announce a special summit, as part of VB2018, that will be dedicated to all aspects of threat intelligence.

VB2018 Small Talk: An industry approach for unwanted software criteria and clean requirements

An industry approach for defining and detecting unwanted software to be presented and discussed at the Virus Bulletin conference.

We have placed cookies on your device in order to improve the functionality of this site, as outlined in our cookies policy. However, you may delete and block all cookies from this site and your use of the site will be unaffected. By continuing to browse this site, you are agreeing to Virus Bulletin's use of data as outlined in our privacy policy.