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
30 July, 2021
Global rank
15
Week rank
24
Month rank
30
IOCs
16494

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 malware by purchasing access to a control dashboard.

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 ransomware 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 the 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 malware in action in interactive virtual machine simulation. Notably, ANY.RUN simulation can be used to view 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 start of 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 ransomware 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?

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

The 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 which contains a 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 take a look inside 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 ransomware 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 ransomware within 20 days and that keys will be deleted.

IOCs

IP addresses
192.168.100.36
204.11.56.48
192.168.100.69
213.186.33.4
209.99.40.222
192.168.100.197
192.168.100.60
192.168.100.175
192.168.100.14
213.186.33.5
192.168.100.17
213.186.33.17
213.186.33.3
192.168.100.117
74.220.199.6
192.168.100.105
66.171.248.178
192.168.100.51
91.195.240.94
192.168.100.217
Hashes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www.imperfectlymassabella.com
www.metaspace.global
www.howtoberealonline.com
www.forevercelebration2026.com
www.astaxanthinsaveme.com
www.thesweetboy.com
www.greensstrings.com
www.influencer.fund
www.mldarby.com
www.peak-valleyadvertising.com
www.prinothhusky.com
wattty.com
www.pourheloise.com
www.refreshlightingcompany.com
www.pateleprevention.com
www.papablogzzi.com
www.a2amc.com
www.dwchongzhi.com
www.genesysshop.com
www.everythingfinesse.com

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