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
18 February, 2020
Global rank
14
Week rank
23
Month rank
24
IOCs
5033

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
103.224.212.222
204.11.56.48
87.98.154.146
213.186.33.17
101.226.226.43
66.171.248.178
35.246.6.109
164.132.235.17
58.251.121.110
213.186.33.16
209.99.64.53
213.186.33.3
69.73.180.151
77.104.171.238
87.236.16.31
92.53.96.201
217.70.184.50
217.160.0.234
192.168.100.135
188.165.53.185
Hashes
a89ff5da7c1c949768bd1f83fede6a02363ec8082b057aa34ea627d4ac81de8a
233437b647f9482a8a3ba51d0af69039bb58fb48609704a39db1f709a0e6aca6
643f8043c0b0f89cedbfc3177ab7cfe99a8e2c7fe16691f3d54fb18bc14b8f45
d77378dcc42b912e514d3bd4466cdda050dda9b57799a6c97f70e8489dd8c8d0
39d000d2c4b8016d4b8efb75ed99272b925a789ef35248e492f51149cc4712a5
2942708537ed2607d9b8787539ca1a9bdea9247c78ef7ece4302df5e5c6e6d00
ca7105c907ddc746eebcc6c845b2a7b4795b4cb9d7ec55972a6ea62aa7bdca9d
9e44a9653ea97f015a183d4b98d9deee6dd59cb664d4992cc0ea815943141ece
a2a1b1e7c281f3b63c37e7eab69b738b3ed6663ecaa427ca36022877b44d0f19
6c1ed5eb1267d95d8a0dc8e1975923ebefd809c2027427b4ead867fb72703f82
af8e74d00babaae01b6f3b137cff7b6a6951456c66ffa95122695dad6c7b41a9
3e33073f2f64ba1af0f31b5e5c617d4c537c9ccd41d6ff7655b1755cc086a719
47c156f0bcc2bba571aa26cd83b49ba835ebe27c554095c4fb38b4e2df483a2d
3b8942d92ad2a01aca3ca281cc3c2b45be0e8a01fa82481cbf090dbfb088cb0a
38f45db824fe556cc1061c9aad40ec9ce58479f339e0dd809b8d8e430d16ed0e
d681ad4ddbd80dde70203bfa9287e734172a4125e15e37914c7322e9491b1750
fec01ecfbc95ba154b19c1e9bb93edaa4bbed6628380b6670afe130e4b05c58b
0452a7ada10bdeda0eb905da0549955f9ce8486ff7cf76a51d73f90a90e89aad
6525a300cb8a121c2476c25ea684aad8d2f9768318d7cc0f90bb7e00e877fdf3
02f3ab4845a3f1c15bb5865214e34285a803ac0757fbe8c15ded028aadc6f4e2
Domains
thuocnam.tk
majul.com
m-onetrading-jp.com
krupskaya.com
isns.net
elx01.knas.systems
corpcougar.com
cloudresemblao.top
garizzlas.top
gifts.wear.sendmenowllc.org
sys.admin.log.burgermen.org
au.big.goodtimenews.org
art.sample.smartgalaxy.org
adonis-medicine.at
news-medias.ru
miska-server.at
gohaiendo.com
datdepot.net
slemend.com
velquene.net

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