RANSOM_AVCRYPT.A

This Ransomware arrives on a system as a file dropped by other malware or as a file downloaded unknowingly by users when visiting malicious sites.

However, as of this writing, the said sites are inaccessible. It deletes itself after execution.

Arrival Details

This Ransomware arrives on a system as a file dropped by other malware or as a file downloaded unknowingly by users when visiting malicious sites.

Installation

This Ransomware drops the following copies of itself into the affected system:

• %Application Data%\{User name}.exe

(Note: %Application Data% is the Application Data folder, where it usually is C:\Documents and Settings\{user name}\Application Data on Windows 2000, Windows Server 2003, and Windows XP (32- and 64-bit); C:\Users\{user name}\AppData\Roaming on Windows Vista (32- and 64-bit), Windows 7 (32- and 64-bit), Windows 8 (32- and 64-bit), Windows 8.1 (32- and 64-bit), Windows Server 2008, and Windows Server 2012.)

It drops the following files:

• %Application Data%\+{Random digits}.bmp - Wallpaper notifying the user that his/her data is encrypted
• %User Temp%\+.bat - Cleans up the logs, processes and files created by the malware
• %User Temp%\t.zip - an archive containing tor.exe and its components
• libeay32.dll - Extracted from t.zip. DLL needed by tor
• libevent_core-2-0-5.dll - Extracted from t.zip. DLL needed by tor
• libevent_extra-2-0-5.dll - Extracted from t.zip. DLL needed by tor
• libevent-2-0-5.dll - Extracted from t.zip. DLL needed by tor
• libgcc_s_sjlj-1.dll - Extracted from t.zip. DLL needed by tor
• libgmp-10.dll - Extracted from t.zip. DLL needed by tor
• libssp-0.dll - Extracted from t.zip. DLL needed by tor
• ssleay32.dll - Extracted from t.zip. DLL needed by tor
• t.bmp - Extracted from t.zip. Will later be moved to %Application Data%\+{Random digits}.bmp
• tor.exe - Extracted from t.zip. Used by malware to contact the C&C server
• zlib1.dll - Extracted from t.zip. DLL needed by tor

(Note: %Application Data% is the Application Data folder, where it usually is C:\Documents and Settings\{user name}\Application Data on Windows 2000, Windows Server 2003, and Windows XP (32- and 64-bit); C:\Users\{user name}\AppData\Roaming on Windows Vista (32- and 64-bit), Windows 7 (32- and 64-bit), Windows 8 (32- and 64-bit), Windows 8.1 (32- and 64-bit), Windows Server 2008, and Windows Server 2012.. %User Temp% is the user's temporary folder, where it usually is C:\Documents and Settings\{user name}\Local Settings\Temp on Windows 2000, Windows Server 2003, and Windows XP (32- and 64-bit); C:\Users\{user name}\AppData\Local\Temp on Windows Vista (32- and 64-bit), Windows 7 (32- and 64-bit), Windows 8 (32- and 64-bit), Windows 8.1 (32- and 64-bit), Windows Server 2008, and Windows Server 2012.)

It adds the following processes:

• tor.exe

It leaves text files that serve as ransom notes containing the following:

• {Folders containing encrypted files}\+HOW_TO_UNLOCK.txt

It adds the following mutexes to ensure that only one of its copies runs at any one time:

• .$

Autostart Technique

This Ransomware adds the following registry entries to enable its automatic execution at every system startup:

HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\
Windows\CurrentVersion\Policies\
Explorer\Run
Windows = %Application Data%\{User name}.exe

HKEY_CURRENT_USER\SOFTWARE\Microsoft\
Windows\CurrentVersion\Policies\
Explorer\Run
Windows = %Application Data%\{User name}.exe

Other System Modifications

This Ransomware adds the following registry keys:

HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\
Windows\CurrentVersion\Uninstall\
Adobe
Default = ""

It modifies the following registry entries:

HKEY_CURRENT_USER\Software\Microsoft\
Windows\CurrentVersion\Explorer\
Advanced
ShowInfoTip = 0

HKEY_CURRENT_USER\Software\Microsoft\
Windows\CurrentVersion\Explorer\
Advanced
FolderContentsInfoTip = 0

HKEY_CURRENT_USER\Software\Microsoft\
Windows\CurrentVersion\Explorer\
Advanced
EnableBalloonTips = 0

HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\
services\Winmgmt
Start = 2

HKEY_CURRENT_USER\Software\Microsoft\
Windows\CurrentVersion\Explorer\
Advanced
StartButtonBalloonTip = 0

HKEY_CURRENT_USER\Software\Microsoft\
Windows\CurrentVersion\Explorer\
Advanced
Hidden = 0

HKEY_CURRENT_USER\Software\Microsoft\
Windows\CurrentVersion\Explorer\
Advanced
ShowSuperHidden = 0

HKEY_CURRENT_USER\Software\Microsoft\
Windows\CurrentVersion\Explorer\
Advanced
HideSCAHealth = 1

HKEY_CURRENT_USER\Software\Microsoft\
Internet Explorer\Download
CheckExeSignatures = no

HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\
Windows\CurrentVersion\Policies\
System
EnableVirtualization = 0

HKEY_CURRENT_USER\Software\Microsoft\
Windows\CurrentVersion\Policies\
Associations
LowRiskFileTypes = .cmd;.exe;.bat;

HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\
Windows\CurrentVersion\Explorer
SmartScreenEnabled = Off

HKEY_LOCAL_MACHINE\SOFTWARE\Policies\
Microsoft\Windows\System
EnableSmartScreen = 0

HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\
Windows\CurrentVersion\Policies\
System
EnableLUA = 0

HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\
Windows NT\CurrentVersion\SystemRestore
RPSessionInterval = 0

HKEY_LOCAL_MACHINE\SOFTWARE\Policies\
Microsoft\Windows Defender\Real-Time Protection
DisableRealtimeMonitoring = 1

HKEY_LOCAL_MACHINE\SOFTWARE\Policies\
Microsoft\Windows Defender
DisableAntiSpyware = 1

HKEY_LOCAL_MACHINE\SOFTWARE\Policies\
Microsoft\Windows Defender\Real-Time Protection
DisableRealtimeMonitoring = 1

HKEY_LOCAL_MACHINE\SOFTWARE\Policies\
Microsoft\Windows\DeviceGuard
EnableVirtualizationBasedSecurity = 0

HKEY_LOCAL_MACHINE\SOFTWARE\Policies\
Microsoft\Windows\DeviceGuard
RequirePlatformSecurityFeatures = 0

HKEY_LOCAL_MACHINE\SOFTWARE\Policies\
Microsoft\Windows\DeviceGuard
HypervisorEnforcedCodeIntegrity = 0

HKEY_LOCAL_MACHINE\SOFTWARE\Policies\
Microsoft\Windows\DeviceGuard
HVCIMATRequired = 0

HKEY_LOCAL_MACHINE\SOFTWARE\Policies\
Microsoft\Windows\DeviceGuard
LsaCfgFlags = 0

It changes the desktop wallpaper by modifying the following registry entries:

HKEY_CURRENT_USER\Control Panel\Desktop
TileWallpaper = 0

HKEY_CURRENT_USER\Control Panel\Desktop
WallpaperStyle = 0

HKEY_CURRENT_USER\Control Panel\Desktop
Wallpaper = %Application Data%\+{Random digits}.bmp

It deletes the following registry keys:

HKEY_CURRENT_USER\Software\Policies\
Microsoft\Windows\System
DisableCMD = 0

(Note: The default value data of the said registry entry is 0.)

HKEY_CURRENT_USER\Software\Microsoft\
Windows\CurrentVersion\Policies\
System
DisableRegistryTools = 0

Backdoor Routine

This Ransomware posts the following information to its command and control (C&C) server:

• Windows version
• Time zone

Other Details

This Ransomware connects to the following URL(s) to check for an Internet connection:

• https://www.microsoft.com

It connects to the following possibly malicious URL:

• {BLOCKED}uupc.onion

It does the following:

• It sets the machine's desktop to the following:
  
• Deletes backup catalog of the affected machine by executing the following command:
  • wbadmin delete catalog -quiet
• It deletes shadow copies by executing the following command:
  
  • wmic shadowcopy delete /nointeractive
• Acquires a list of antivirus products installed in the system through the following WQL data query:
  • SELECT * FROM AntiVirusProduct
• Uninstalls any antivirus product installed in the system via the following command
  
  • wmic product where ( Vendor like "%{AV product name}%" ) call uninstall /nointeractive
• It deletes services by executing the following commands:
  • sc config config "MBAMService" start= disabled
  • sc config stop "MBAMService"
  • sc config delete "MBAMService"
  • sc config config "MBAMSwissArmy " start= disabled
  • sc config stop "MBAMSwissArmy "
  • sc config delete "MBAMSwissArmy "
  • sc config config "MBAMChameleon " start= disabled
  • sc config stop "MBAMChameleon "
  • sc config delete "MBAMChameleon "
  • sc config config "MBAMWebProtection" start= disabled
  • sc config stop "MBAMWebProtection"
  • sc config delete "MBAMWebProtection"
  • sc config config "MBAMFarflt" start= disabled
  • sc config stop "MBAMFarflt"
  • sc config delete "MBAMFarflt"
  • sc config config "ESProtectionDriver" start= disabled
  • sc config stop "ESProtectionDriver"
  • sc config delete "ESProtectionDriver"
  • sc config config "MBAMProtection" start= disabled
  • sc config stop "MBAMProtection"
  • sc config delete "MBAMProtection"
  • sc config config "Schedule" start= disabled
  • sc config stop "Schedule"
  • sc config delete "Schedule"
  • sc config config "WPDBusEnum" start= disabled
  • sc config stop "WPDBusEnum"
  • sc config delete "WPDBusEnum"
  • sc config config "TermService" start= disabled
  • sc config stop "TermService"
  • sc config delete "TermService"
  • sc config config "SDRSVC" start= disabled
  • sc config stop "SDRSVC"
  • sc config delete "SDRSVC"
  • sc config config "RasMan" start= disabled
  • sc config stop "RasMan"
  • sc config delete "RasMan"
  • sc config config "PcaSvc" start= disabled
  • sc config stop "PcaSvc"
  • sc config delete "PcaSvc"
  • sc config config "MsMpSvc" start= disabled
  • sc config stop "MsMpSvc"
  • sc config delete "MsMpSvc"
  • sc config config "SharedAccess" start= disabled
  • sc config stop "SharedAccess"
  • sc config delete "SharedAccess"
  • sc config config "wscsvc" start= disabled
  • sc config stop "wscsvc"
  • sc config delete "wscsvc"
  • sc config config "srservice" start= disabled
  • sc config stop "srservice"
  • sc config delete "srservice"
  • sc config config "Schedule" start= disabled
  • sc config stop "Schedule"
  • sc config delete "Schedule"
  • sc config config "VSS" start= disabled
  • sc config stop "VSS"
  • sc config delete "VSS"
  • sc config config "swprv" start= disabled
  • sc config stop "swprv"
  • sc config delete "swprv"
  • sc config config "WerSvc" start= disabled
  • sc config stop "WerSvc"
  • sc config delete "WerSvc"
  • sc config config "MpsSvc" start= disabled
  • sc config stop "MpsSvc"
  • sc config delete "MpsSvc"
  • sc config config "WinDefend" start= disabled
  • sc config stop "WinDefend"
  • sc config delete "WinDefend"
  • sc config config "wuauserv" start= disabled
  • sc config stop "wuauserv"
  • sc config delete "wuauserv"
• Changes the affected machine’s boot configuration by executing the following commands:
  
  • bcdedit /timeout 0
  • bcdedit /set {bootmgr} displaybootmenu no
  • bcdedit /set {default} bootems off
  • bcdedit /set {default} advancedoptions off
  • bcdedit /set {default} optionsedit off
  • bcdedit /set {default} bootstatuspolicy ignoreallfailures
  • bcdedit /set {default} recoveryenabled No
• It avoids encrypting files with the following extensions:
  • .kdmp
  • .lnk
  • .manifest
  • .mkv
  • .mp3
  • .msi
  • .png
  • .sam
  • .scr
  • .sys
  • .temp
  • .theme
  • .ttf
  • .url
  • .vdx
  • .vxd
  • .wav
  • .wim
  • .avi
  • .bat
  • .cab
  • .chm
  • .cmd
  • .com
  • .cpl
  • .dll
  • .dmp
  • .evtx
  • .exe
  • .flv
  • .folder
  • .gif
  • .ico
  • .inf
  • .ini

However, as of this writing, the said sites are inaccessible.

It deletes itself after execution.

It does not proceed to its malicious routine if it detects that it is being debugged.

Ransomware Routine

This Ransomware avoids encrypting files found in the following folders:

• drm
• sendto
• i386
• perl
• boost
• config.msi
• system volume information
• programfiles(x86)
• windows
• appdata
• programdata
• programfiles
• $recycle.bin
• windows.old
• $windows.~bt
• driver
• boot
• winsxs
• driverstore
• cache2
• httpcache
• cookieshistory
• ie5
• internet explorer
• firefox
• chrome
• opera
• content.ie5
• node_modules
• applicationdata
• nvidia
• intel
• microsoft
• music
• song
• sample pictures
• sample videos
• sample media
• local settings
• prefetch
• winnt
• readme
• spider
• preflogs
• recycle
• recycler
• movies
• cookies
• localservice
• default
• xampp

It renames encrypted files using the following names:

• +{original file name}

It leaves text files that serve as ransom notes containing the following text:

• lol n