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Backdoor.Mevade

Risk Level 1: Very Low

Discovered:
September 5, 2013
Updated:
September 9, 2013 5:45:22 PM
Type:
Trojan
Infection Length:
Varies
Systems Affected:
Windows 2000, Windows 7, Windows Vista, Windows XP
Once executed, the Trojan checks to see if it is being run in a virtual machine by searching for the following programs:
  • VirtualBox
  • VMWare
  • Sandboxie

The Trojan then copies itself to the following location:
%System%\config\systemprofile\Local Settings\Application Data\Windows Internet Name Service\wins.exe

It then creates the following files:
  • %ProgramFiles%\Tor\tor.exe
  • %System%\config\systemprofile\Local Settings\Application Data\Windows Internet Name Service\049e7fb749be2cdf169e28bb0a27254f\181084e525a65ef540c63d60ce07f836.ct
  • %System%\config\systemprofile\Local Settings\Application Data\Windows Internet Name Service\049e7fb749be2cdf169e28bb0a27254f\181084e525a65ef540c63d60ce07f836.ph
  • %System%\config\systemprofile\Local Settings\Application Data\Windows Internet Name Service\cache.00
  • %System%\config\systemprofile\Local Settings\Application Data\Windows Internet Name Service\queries-02.cache
  • %SystemDrive%\Documents and Settings\LocalService\Application Data\tor\lock
  • %SystemDrive%\Documents and Settings\LocalService\Application Data\tor\state

Next, the Trojan creates the following registry entries to register itself as system services:
  • HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\Windows Internet Name Service\"Description" = "Provides Internet Name Service"
  • HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\Windows Internet Name Service\"DisplayName" = "Windows Internet Name Service"
  • HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\Windows Internet Name Service\"ErrorControl" = "1"
  • HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\Windows Internet Name Service\"FailureActions" = "[BINARY DATA]"
  • HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\Windows Internet Name Service\"Group" = "netsvcs"
  • HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\Windows Internet Name Service\"ImagePath" = "%System%\config\systemprofile\Local Settings\Application Data\Windows Internet Name Service\wins.exe"
  • HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\Windows Internet Name Service\"ObjectName" = "LocalSystem"
  • HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\Windows Internet Name Service\"Start" = "2"
  • HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\Windows Internet Name Service\"Type" = "16"
  • HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\Windows Internet Name Service\Security\"Security" = "[BINARY DATA]"
  • HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\tor\"Description" = "Provides an anonymous Internet communication system"
  • HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\tor\"DisplayName" = "Tor Win32 Service"
  • HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\tor\"ErrorControl" = "0"
  • HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\tor\"ImagePath" = ""%ProgramFiles%\Tor\tor.exe\" --nt-service \"-ControlPort\" \"9051""
  • HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\tor\"ObjectName" = "NT AUTHORITY\LocalService"
  • HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\tor\"Start" = "2"
  • HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\tor\"Type" = "16"
  • HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\tor\Security\"Security" = "[BINARY DATA]"

The services have the following characteristics:
Startup Type: Automatic
Image Path: %ProgramFiles%\Tor\tor.exe\" --nt-service \"-ControlPort\" \"9051"
Display Name: Tor Win32 Service

Startup Type: Automatic
Image Path: %System%\config\systemprofile\Local Settings\Application Data\Windows Internet Name Service\wins.exe
Display Name: Windows Internet Name Service

It then creates the following registry entries to register itself as a legacy driver service:
  • HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Enum\Root\LEGACY_TOR\"NextInstance" = "1"
  • HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Enum\Root\LEGACY_TOR\0000\"Class" = "LegacyDriver"
  • HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Enum\Root\LEGACY_TOR\0000\"ClassGUID" = "{8ECC055D-047F-11D1-A537-0000F8753ED1}"
  • HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Enum\Root\LEGACY_TOR\0000\"ConfigFlags" = "0"
  • HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Enum\Root\LEGACY_TOR\0000\"DeviceDesc" = "Tor Win32 Service"
  • HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Enum\Root\LEGACY_TOR\0000\"Legacy" = "1"
  • HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Enum\Root\LEGACY_TOR\0000\"Service" = "tor"
  • HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Enum\Root\LEGACY_WINDOWS_INTERNET_NAME_SERVICE\"NextInstance" = "1"
  • HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Enum\Root\LEGACY_WINDOWS_INTERNET_NAME_SERVICE\0000\"Class" = "LegacyDriver"
  • HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Enum\Root\LEGACY_WINDOWS_INTERNET_NAME_SERVICE\0000\"ClassGUID" = "{8ECC055D-047F-11D1-A537-0000F8753ED1}"
  • HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Enum\Root\LEGACY_WINDOWS_INTERNET_NAME_SERVICE\0000\"ConfigFlags" = "0"
  • HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Enum\Root\LEGACY_WINDOWS_INTERNET_NAME_SERVICE\0000\"DeviceDesc" = "Windows Internet Name Service"
  • HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Enum\Root\LEGACY_WINDOWS_INTERNET_NAME_SERVICE\0000\"Legacy" = "1"
  • HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Enum\Root\LEGACY_WINDOWS_INTERNET_NAME_SERVICE\0000\"Service" = "Windows Internet Name Service"

The threat then creates the following registry entries:
  • HKEY_LOCAL_MACHINE\SECURITY\Policy\Secrets\_SC_tor\"(Default)" = "4"
  • HKEY_LOCAL_MACHINE\SECURITY\Policy\Secrets\_SC_tor\SecDesc\"(Default)" = "[BINARY DATA]"

It then modifies the following registry entry to alter Explorer settings:
HKEY_USERS\.DEFAULT\Software\Microsoft\Windows\CurrentVersion\Explorer\Shell Folders\"Local AppData" = "%SystemDrive%\Documents and Settings\LocalService\Local Settings\Application Data"

The Trojan then connects to one of following remote servers on the Tor network:
  • pomyeasfnmtn544p.onion
  • ijqqxydixp4qbzce.onion
  • 7fyipi6vxyhpeouy.onion
  • onhiimfoqy4acjv4.onion
  • 6tlpoektcb3gudt3.onion
  • qxc7mc24mj7m4e2o.onion
  • lqqciuwa5yzxewc3.onion
  • wsytsa2omakx655w.onion
  • lqqth7gagyod22sc.onion
  • lorpzyxqxscsmscx.onion
  • mdyxc4g64gi6fk7b.onion
  • ye63peqbnm6vctar.onion
  • 7sc6xyn3rrxtknu6.onion
  • l77ukkijtdca2tsy.onion

Recommendations

Symantec Security Response encourages all users and administrators to adhere to the following basic security "best practices":

  • Use a firewall to block all incoming connections from the Internet to services that should not be publicly available. By default, you should deny all incoming connections and only allow services you explicitly want to offer to the outside world.
  • Enforce a password policy. Complex passwords make it difficult to crack password files on compromised computers. This helps to prevent or limit damage when a computer is compromised.
  • Ensure that programs and users of the computer use the lowest level of privileges necessary to complete a task. When prompted for a root or UAC password, ensure that the program asking for administration-level access is a legitimate application.
  • Disable AutoPlay to prevent the automatic launching of executable files on network and removable drives, and disconnect the drives when not required. If write access is not required, enable read-only mode if the option is available.
  • Turn off file sharing if not needed. If file sharing is required, use ACLs and password protection to limit access. Disable anonymous access to shared folders. Grant access only to user accounts with strong passwords to folders that must be shared.
  • Turn off and remove unnecessary services. By default, many operating systems install auxiliary services that are not critical. These services are avenues of attack. If they are removed, threats have less avenues of attack.
  • If a threat exploits one or more network services, disable, or block access to, those services until a patch is applied.
  • Always keep your patch levels up-to-date, especially on computers that host public services and are accessible through the firewall, such as HTTP, FTP, mail, and DNS services.
  • Configure your email server to block or remove email that contains file attachments that are commonly used to spread threats, such as .vbs, .bat, .exe, .pif and .scr files.
  • Isolate compromised computers quickly to prevent threats from spreading further. Perform a forensic analysis and restore the computers using trusted media.
  • Train employees not to open attachments unless they are expecting them. Also, do not execute software that is downloaded from the Internet unless it has been scanned for viruses. Simply visiting a compromised Web site can cause infection if certain browser vulnerabilities are not patched.
  • If Bluetooth is not required for mobile devices, it should be turned off. If you require its use, ensure that the device's visibility is set to "Hidden" so that it cannot be scanned by other Bluetooth devices. If device pairing must be used, ensure that all devices are set to "Unauthorized", requiring authorization for each connection request. Do not accept applications that are unsigned or sent from unknown sources.
  • For further information on the terms used in this document, please refer to the Security Response glossary.
Writeup By: Dumitru Stama
Summary| Technical Details| Removal

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