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
15 April, 2021
Global rank
15
Week rank
24
Month rank
30
IOCs
13450

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
192.168.100.81
192.168.100.79
192.168.100.8
192.168.100.77
192.168.100.157
192.168.100.58
192.168.100.26
192.168.100.192
192.168.100.36
66.171.248.178
192.168.100.116
192.168.100.11
192.168.100.183
192.168.100.213
192.168.100.240
213.186.33.4
192.168.100.104
209.99.40.222
204.11.56.48
192.168.100.147
Hashes
d77378dcc42b912e514d3bd4466cdda050dda9b57799a6c97f70e8489dd8c8d0
8910554f04d8a7626904328f504b4d0f5c084cbeed4867b173447ec32195c3b5
fd1096cb5bedfa8eb0bc020ec86133c26e2f3476d7d90ad4ff768352ce5c1e64
7fd660894a473fe94690eb5f63adefac02379960ac1b828418d6cdb3b06ecedb
84515aca22285b5ee747248d21d2528fd6848fa249fd752541d42a4232610220
233437b647f9482a8a3ba51d0af69039bb58fb48609704a39db1f709a0e6aca6
df957cb8bd42d4db04c3d3104d045f50f5871141a08f76c204fca5de8d25bbeb
ce093ffa19f020a2b73719f653b5e0423df28ef1d59035d55e99154a85c5c668
6c1ed5eb1267d95d8a0dc8e1975923ebefd809c2027427b4ead867fb72703f82
098aad386b0f549cefddf2001dba9f31f40d88a3618cd3a8d5589b4b0b467342
c47c4e7cde2a0202935b9b7333d252dc509d4d13b0cffe81d0103981afad12ab
238d1b406e8d6434016e4a850c4c7ad4cbc96b844842824175eb20dc0b662fe9
2a0fdc6d7e3873cc6f371b6a56ccd50fa67d75a64b819702313ce195bc15fb01
1ea8ac0550b24ef140a597a9f26e9cfc4dee146693a685692f850182b92700d7
759284272f3abbf46b9464e6484f60b808f19814afd17f5447bff1cfe8e10b47
c09c6ebebf311bbe3ac421d286f419e2d0c3707229fa1d936793290f8eeb3a5b
047d9e46f401f06f008d2c4eafcdbbb0fcf9d34c8abcce30966475397dd46784
9b908b006d12e553d636e69e54ee1bbdf630199c02c56c2be8edddc5a66e69a3
be7ce0b23d6ee4326e909ef32d0ceda66f762a8c37fd239268e45d11e36ee620
e0edd00203acc80dfeb3121dfe150c1fa5cbc6341b3cdeb1e8271adbc9d7be5c
Domains
www.nativo.com
tp00.everesttech.net.akadns.net
booking.msg.bluhotels.com
booking.msg.bluhotels.com
mail.valoracap.com
alkhanservice.com
hellrieqel.com
www.santanutoursandtravels.com
www.koratnana.com
www.nusushibar.com
www.assistirtvbr.tv
shop.detanux.com
fuseplatform.com
oththukaruva.com
proffteplo.com
topautoinsurers.net
bozarkaya.com
mrkluttz.com
aigoingtokill.airobotheworld.com
www.winnexa.com

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