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
4 October, 2022
Global rank
16
Week rank
33
Month rank
30
IOCs
50932

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 like Troldesh or Nemty, 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
192.168.100.124
186.202.157.79
192.168.100.166
192.168.100.6
192.168.100.202
192.168.100.23
192.168.100.157
185.135.88.105
192.168.100.156
172.67.193.175
192.168.100.22
192.168.100.215
66.96.147.106
192.168.100.24
192.168.100.71
192.168.100.72
192.168.100.63
192.168.100.232
192.168.100.218
192.168.100.176
Hashes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zebra.wthelpdesk.com
zerit.top
fuyt.org
tzgl.org
kotob.top
securebiz.org
td-balancer-euw3-251-130.wixdns.net
t.hwqloan.com
www.thecitizensforum.org
xakfor.net
wrrst.top
tbpws.top
astdg.top
na1.documents.adobe.com
serviclubypf.com
www.covidworld.info
paymenthacks.com
os.thedownloadmanagerapp.com
funbe25.com
cdn.jsdeliver.net

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