Do Math or Windows Dies! – customizing a .NET ransomware

NOTE: the content of this article is educational and informative. The goal is to learn how malware works and how can we identify its capabilities. The author is not responsible for any bad actions derived from the information of the post. The author does NOT ENCOURAGE to execute the sample OUTSIDE OF AN ISOLATED LABORATORY.

In this article we are going to analyze, gut and customize a little screen-locker (a member of ransomware family that locks the machine without encrypt the data). This is a clumsy but effective sample that we will alter to create our own ScreenLocker.

SSHBOT, the cr*ppy ScreenLocker

SSHBOT, also known as P4YME, is an old and unsophisticated malware from ransomware family.

We will use a public sample submited to VirusTotal, where is detected by 54 Anti-virus:

When executed, it restarts the machine and shows this message:

[Read more…]

Analysis of Linux.Haikai: inside the source code

A few days ago we got the source code of the Haikai malware, which corresponds to one of the many implementations carried out by the continuous recycling of source code belonging to different IoT botnets. Although we have not identified any new developments compared to previous IoT malware versions, it has allowed us to obtain a lot of information on techniques, improvements and authors.

It should also be noted that, according to different records obtained, this botnet has been in operation for most of the last month of June.

In the following lines the code will be analyzed, as well as the possible attributions and the implementations not referenced in the execution thread, which allow us to guess that the code is mutating in different lines in parallel for the same function.

So let’s start by analyzing the structure of the files. [Read more…]

‘Reversing’ of malware network protocols with ‘angr’

One of the most difficult objectives to obtain in the analysis of a malicious binary is usually discovering all of the functionalities that it has. If in addition, these functions are only executed at the discretion of the attackers through its control center, things get complicated. For various reasons, many times we cannot carry out a full dynamic analysis, such as the fall of the malware infrastructure or the isolation of the sample to avoid contact with the C&C. In these cases the analysis of the interaction between the server of the attacker and the sample is usually slower, since you have to create a fictitious server or be continually patching/deceiving the sample, to take it through all the different paths that we want to investigate. Depending on the size and complexity of the analyzed code or the objective of the analysis, this task can vary its difficulty and extension over time.

I am going to propose a study example of the functionalities of a fictitious RAT that can be executed according to the orders received from your C&C panel. Our goal would be to create a server that simulates the attacker’s. For this we have to understand the communication protocol between the server and the sample installed on the victim’s device.

[Read more…]

Analysis of Linux.Okiru

In keeping with our campaign of detection and documentation of IoT botnets, a few days ago we found another threat not classified before. It was first uploaded to the VirusTotal platform on November 3 and is only detected as malicious by 4 antiviruses.

During the article, two variants of the malware will be analyzed, which differ fundamentally in their propagation. The first one was detected in our honeypot systems (specifically for the SPARC architecture). The second one is a variant of the first, which was found under the Intel x86_64 architecture, and which the Netlab360 malware lab echoed a few days ago.

As no records of its identification were found, we decided to classify it as Linux.Okiru, due to the name of its binaries.
[Read more…]

Droppers from Locky Ransomware with extra anti-Sandboxing

Recently an old acquaintance has returned to his old ways. This is the Ransomware “Locky”, which about a year ago was very active through #Malspam campaigns (Spam Mail with the purpose of installing malware in the victim’s system) mostly with scripting files such as “.js “,” .wsf “or” .vbe “. Since then it has continued to maintain activity, although to a lesser extent.
Recently they have started a new campaign in which they use .doc (MSOffice Word) files with macros, like the following:

[Read more…]

Analysis of Linux.Helios

For several weeks we have been detecting a new variant of malware for Linux and IoT architectures from the malware laboratory of S2 Grupo, registered for the first time on the VirusTotal platform on October 18, which we have called Linux.Helios, due to the name of certain functions present in the sample.

We emphasize that the main antivirus signatures do not unanimously classify this sample: they range from ELF.DDoS to Tsunami, through Gafgyt or Mirai.
[Read more…]

The mimi (mimikatz) side of #NotPetya

(Please note some of the internal links are in Spanish)
One of the things that most caught our attention from the #NotPetya malware lab is the module that appears to contain code from the mimikatz tool. It is an automation of the process of any pentest that we believe is worth studying and treat it with love, to learn.
For the analysis we focus on the 32-bit version of the binary:
[Read more…]

The Evolution of Trickbot

From the malware lab of S2 Grupo we have been monitoring the movements of a Trojan known as Trickbot. Its relationship with Dyre, another older Trojan with which it shares many design features, and the speed at which it evolves, has captured our interest ever since we saw the first samples.

This malware is usually categorized as a banking Trojan since it has so far been very oriented towards data theft relating to banking, but its modular design allows to expand its capabilities at any time so as to perform any kind of extra action.

During its early versions, some very good analyses were already done such as those of @hasherezade in the malwarebytes blog and Xiaopeng Zhang in that of Fortinet. But the development of Trickbot has continued during the last few months, reaching version 17 in less than 6 months. So we thought that it would be interesting to check the changes it has undergone during its evolution and to delve deeper into some of its most curious techniques when performing different actions.
[Read more…]

Shadow Brokers: exploiting Eternalblue + Doublepulsar

(Just one month after publishing this post in spanish, these exploits were used in conjunction with the WanaCry ransomware to perform one of the largest worldwide cyber attacks of the last few years.
Hundreds of companies (Hospitals too) were compromised and all their data was encrypted.)

A few days ago the news broke out that the group Shadow Brokers had released a new batch of exploits of the NSA. As if this were not enough, in the github where the exploits are there is also information on how to attack the banking systems.

The vast majority of published exploits make compromising a Windows system childlike and almost as we see in movies, since they are several 0-day (now patched by Microsoft) that attack the SMB protocol in all its versions.

Of all the exploits available, the one that has drawn the most attention to the community has been the combo called Eternalblue + Doublepulsar. In this post we will explain how to deploy a test environment where you can test the exploits.

(Editor’s note: Needless to say, the information is provided for informational and didactic purposes in order to collaborate in improving the knowledge of cybersecurity technicians. Cybercriminals do not need anyone to teach them how to use exploits, and to those unsuspecting scriptkiddies who think of playing cybercriminals, well, good luck in the courts).
[Read more…]

Malware Trends. December 2016

During this month of December we have observed from the malware laboratory of S2 Grupo various threats that we once again wanted to share with you. In this type of entries we will find known threats, seen in other sources or analyzed directly in our laboratory, but the goal of the post is to know what kind of threats have been active throughout this last month.

Here is a diagram with the information collected this month from the lab:


First of all, we would like to highlight the break that Locky has at least given us this month, with a tremendously reduced SPAM compared to the previous two months. This does not mean at all that it has disappeared, rather, many have been arriving at emails with texts of “subject:” such as the following: [Read more…]