GandCrab

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.

  • Type
    Ransomware
  • Origin
    ex-USSR territory
  • First seen
    26 January, 2018
  • Last seen
    20 November, 2019
Global rank
12
Week rank
16
Month rank
22
IOCs
3293

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 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 take a look inside Gandcrab ransom note 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 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
213.186.33.4
213.186.33.3
91.195.240.94
213.186.33.17
66.171.248.178
204.11.56.48
213.186.33.16
164.132.235.17
37.17.224.96
209.99.64.51
87.98.154.146
199.34.228.70
213.186.33.5
188.165.53.185
74.220.199.8
35.246.6.109
185.103.243.59
209.99.40.222
217.70.184.50
103.224.212.222
Hashes
2dc863f32f27866fc6fed640e1c994e6c58976983018acdb9b84a381fb154454
8693739465db3baacb1101aa654759c98768866265e273ea80ffa9751390e459
3f4bec1e395c1fda66a67ae5b9348998ec2a23e714eb5d5f51d9018c0aad7495
2986cdda59c99b1768ebe507c97821444a238faecf0b21aacea68d5ee7b24016
233437b647f9482a8a3ba51d0af69039bb58fb48609704a39db1f709a0e6aca6
37933f3fe03bf3da37a18753e6ec082ad0413f83d9d4402687e5c13a9c20eee5
06872dacbd3b92827ca80a2c3bea4232d6e42afabeb666db5e91cc83bbb298cd
01e1c1b2cf39303184fe75316fce6b3138c353735365fa635dc265e628f6945c
3051aada3a114e46a7dad7445c1263fc8f8e4209d777a51cf3b57827b4abaee2
6dc96391cb620a65eccac3e6ccbde23a814e0398987a251fc6172c63849cfc2f
0f1100bd1f98124187439683f8677b7bb780574cbb81c4e1c405874dd1cccd1c
e06d8ab913e664dfa7fee37a49974febcd3422a67c53c1c08d6a58d8f31b429e
a610cc856f3526b8a3f3da159b244848cc102f03eac6ec5c157b0b276f7b027b
9f7f6130ce051ac93604d0ef7c5f48164fd46007a0bf6895f31830f98e42db2d
643f8043c0b0f89cedbfc3177ab7cfe99a8e2c7fe16691f3d54fb18bc14b8f45
7c486d889f303294b93d93f1dc5c2a8306a9e871d1b165108b39f8ce285f4710
dbadd2cfe55cb9b26fce2dc99aad84816f1f0bf8e5ab014af3bb396089000e45
2bdd05e312dcb925486d3a7750962661946e086c80239c5c4e5098324fc2fe43
aa71b04384d7309c4ca37d76eb1a462c20276ae789c87f7afb0be88a3e365e0d
2c6f2bbe4aa593c5847df89501dcbf481bd58b085868eb767033b2b672a3f2eb
Domains
majul.com
isns.net
zxciuniqhweizsds.com
zonealarm.bit
carder.bit
ransomware.bit
specialtravels.org
gangfans.org
primetimer.org
tokotikotoko.pw
sell.responderbonds.com
cloudresemblao.top
home.webadmin.syscoinc.org
accounts.jumpinghouse.org
sys.admin.log.burgermen.org
au.big.goodtimenews.org
art.sample.smartgalaxy.org
adonis-medicine.at
instant-payments.ru
gohaiendo.com

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