GandCrab

GandCrab is probably one of the most famous Ransomware. A Ransomware is a malware that asks the victim to pay money in order to restore access to encrypted files. If the user does not cooperate the files are forever lost.

Type
Ransomware
Origin
ex-USSR territory
First seen
26 January, 2018
Last seen
20 October, 2021
Global rank
19
Week rank
17
Month rank
12
IOCs
23566

What is GandCrab ransomware?

GandCrab is a ransomware-type malware, which means that it encrypts files on infected machines and demands a ransom in cryptocurrency to restore the lost data. What’s more, this particular strain is distributed as a Ransomware-As-A-Service, allowing anybody to use this program by purchasing access to a control dashboard.

A unique business model and constant updates of the malware, in turn, helped GandCrab to become one of the most widely spread ransomware of 2018.

General Description of GandCrab

Since its discovery on January 26, 2018, at least 5 versions of GandCrab were created. The authors of the program are extremely active and respond to created countermeasures almost instantly, making GandCrab an elusive malware that continues to terrorize private and corporate victims today.

The last identified version of the malware is 5.1 and it targets users from all over the world with one exception – having originated in an ex-USSR country GandCrab is known to ignore users from X-USSR territories, identifying them by the keyboard or UI language settings. Only Windows operating systems are affected by ransomware.

It should be noted, that the virus is assigned a different name by various antivirus software:

  • Ransom: Win32/GandCrab
  • Trojan.Ransom.GandCrab
  • Win32/Filecoder.GandCrab
  • Ransom.GandCrab
  • Trojan-Ransom.Win32.GandCrypt

Usually infecting users through mail spam or exploit kits, the ransomware redirects victims to a TOR website after the files on a victim’s PC are encrypted. For the newer versions of the malware, the only way of restoring the data is through paying the ransom, the amount of which usually fluctuates between 1000 and 3000 dollars. However, some victims, have reported that they were asked to pay as much as 700,000 USD.

Having a RaaS ( Ransomware-as-a-Service ) business model, GandCrab is distributed by the original creators to “clients”, who then deliver the malware to end victims, asking for a custom ransom amount through one of the unique features of the virus – customizable ransom notes. A percentage of the “revenue” is then shared with the malware authors, once a ransom is secured.

GandCrab malware analysis

ANY.RUN provides the ability to watch the GandCrab program in action in interactive virtual machine simulation. Notably, ANY.RUN simulation can be used to perform the analysis of the stages of the virus life cycle:

  • Infection. A victim downloads and opens infected Microsoft Office file which contains a script programmed to download and start the execution of the virus;
  • Execution and information gathering. After the script has started the execution process, GandCrab collects information about the user. At this stage, the execution of the virus is stopped if a Russian keyboard layout or user interface is detected;
  • The malware checks for the presence of antivirus drivers and stops all processes that involve files that it wants to encrypt;
  • The ransomware decrypts the ransom record held in the binary;
  • Next, a key pair is generated;
  • The virus enumerates file and decryptors;
  • GandCrab proceeds to encrypt the files;
  • The malware establishes communication with the server;
  • After that, the malware will try to delete all shadow copies;
  • Finally, a ransom note is displayed to the user.

wallpaper after infection by gandcrab ransomware

Figure 1: Some versions of GandCrab are known to change the desktop wallpaper. This function is omitted in version 5.0.

ransomnote displayed by gandcrab v5.1

Figure 2: A ransomware note displayed by GandCrab v5.1

The following contamination processes are launched by the ransomware:

  • Starts CMD.EXE for commands execution
  • Executes PowerShell scripts
  • Downloads executable files from the Internet
  • Connects to CnC server
  • Makes registry changes
  • Runs wmic.exe
  • Executes vssvc.exe
  • Deletes shadow copies
  • Runs NOTEPAD.EXE

The whole contamination process can be seen in a video, displaying the ANY.RUN simulation.

gandcrab execution process graph

Figure 3: Illustrates the processes launched by GandCrab during its life cycle.

To build itself into the system, GandCrab starts with decrypting an extension name record that is held in the binary. By going through logical drives from “a” to “z” the malware separates all drives that are equal to 0x2 and not equal to 0x5, creating and separating thread to enumerate and encrypt all data that is prepared for encryption. After the encryption is complete, the malware uses wmic to erase all shadow copies. As a result, all data remains affected by the program even after a reboot.

The ransomware leaves behind artifacts that can help to recognize the version. Those exist in the form of extensions of encrypted files.

  • Version 1 gives the .gdcb extension
  • Version 2 and 3 give the .crab extension
  • Version 4 gives the .krab extension
  • Version 5 gives a randomized 5 or more letter extension

How to avoid infection by GandCrab?

According to the analysis, creators of GandGrab patch all exploits in the malware code fairly quickly, which makes the development of countermeasures tricky. Upon contamination with on of the latest versions, the only way to restore the lost data is to pay the ransom. Thus, the best way to stay safe is to prevent contamination.

  • By keeping digital copies of important files in multiple places
  • By making sure that the antivirus software is reliable and updated
  • Avoiding digital downloads on suspicious or unknown websites
  • Avoiding opening the attached files in emails, especially those coming from unknown senders.
  • And not paying the ransom if infected.

That said, effective countermeasures do exist for older versions of the ransomware, including free decrypters and Killswitches. Most notably, a Killswitch for GandCrab v4.1.2 was developed by a cyber threat analysis and response company Ahnlab. The defensive application exploits the mechanics of GandCrab ransomware by creating a file with the .lock extension, which simulates the files that GandCrab itself generates and uses to check whether the victim's computer is included in the record of previously affected machines to avoid double decryption.

The execution of the ransomware stops upon discovery of .lock file if it is placed in %Application Data% for Windows versions before Windows 7 and in %ProgramData% directory for newer OS versions. Even in cases when the malware has already activated, the killswitch will prevent some of the damage.

Interestingly, in response to the killswitch, the GandCrab authors released an exploit, targeting the Ahnlab antivirus software. The exploit was introduced in version v4.2.1 and v4.3 of the malware but did not cause sufficient harm to the antivirus users.

For versions 1, 4 and up through 5.1 there are free decryption tool from Bitdefender.

Distribution of GandCrab

Based on the analysis, ransomware is known to utilize multiple attack vectors, however, compromised list and spam email campaigns are the most commonly used delivery channels. Being delivered to users in spam emails, GandCrab tricks users into downloading a ZIP archive that contains a script file that triggers the download and execution.

GandCrab execution process

An illustration of an execution process can be found below.

gandcrab execution process tree

Figure 4. Analysis of the GandCrab execution process in ANY.RUN

The following behavioural activities are shown in ANY.RUN’s report.

text report of the gandcrab ransomware analysis

Figure 5: A text report created in ANY.RUN

During the execution the malware creates several artifacts that can be viewed in detail in the ANY.RUN simulation.

With file encryption being the main goal of the payload, the malware launches a command line with pre-specified parameters after opening a Microsoft Word file. Startup powershell is then sent as command line parameters, followed by downloading and launching the executable file from the Internet.

How to detect Gandcrab using ANY.RUN?

You can perform the analysis of files using ANY.RUN's "Static Discovering". Open either "Files" tab in the lower part of the task's window or click on the process and then on the button "More Info" in the appeared window. After that, all you need to do is just click on the file.

gandcrab ransom note

Figure 6: Gandcrab ransom note

Conclusion

Thanks a unique business model which involves selling the program as a service and defining characteristics like customizable ransom notes, GandCrab’s popularity quickly escalated in 2018, making the virus the most widely spread ransomware of the year.

Unfortunately, the creators proved to be very active and continued to respond quickly to all attempts to create effective countermeasures. While adhering to common practices of staying safe on the internet decreases the probability of getting attacked greatly, running interactive sandbox simulations in a service such as ANY.RUN is the best way to ensure personal or corporate safety.

P.S.

On the 1st June 2019 creators of the GandCrab ransomware made a post in which they stating that they have generated more than $2 billion in ransom payments, with average weekly payments of $2.5 million dollars. They also said that they have personally earned $150 million, which they have cashed out and invested in legal business entities. In the same post, they announced about ending of distributing the program within 20 days and that keys will be deleted.

IOCs

IP addresses
192.168.100.15
66.171.248.178
192.168.100.239
204.11.56.48
192.168.100.107
35.205.61.67
35.242.251.130
192.168.100.232
192.168.100.149
209.99.40.222
192.168.100.168
192.168.100.168
192.168.100.44
192.168.100.39
213.186.33.4
192.168.100.200
192.168.100.65
192.168.100.190
192.168.100.82
192.168.100.173
Hashes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isns.net
bulkbacklinks.com
www.risal.com
www.liaphone.com
www.mambomakaya.com
sandynjrelieffund.org
seeyouonlineservice.com
qxq.ddns.net
www.allvegangoods.com
aeifaeifhutuhuhuso.io
xfhoahegue.ru
gohaiendo.com
weekdanys.com
com-edit.fr
sefuhsuifhishf.ru
skomdoornsqmui.eu
www.nerdirect.net
parentallsocket.info
cldfnt.net
ozvision.ozsn.net

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