Threat Description

Worm:​W32/AutoRun.GM

Details

Category: Malware
Type: Worm
Platform: W32

Summary



A standalone malicious program which uses computer or network resources to make complete copies of itself. May include code or other malware to damage both the system and the network.



Removal



Automatic Disinfection

Allow F-Secure Anti-Virus to disinfect the relevant files.

For more general information on disinfection, please see Removal Instructions.



Technical Details



Execution

Upon execution, the malware first creates a copy of itself in the program files, then amends the registry to ensure automatic execution.

It also creates the following files in all removable drives found in the system:

  • system.exe
  • autorun.inf

The system.exe file is a copy of itself, while the autorun.inf contains the following strings:

  • [autorun]open=system.exeshellexecute=system.exeshell\Explore\command=system.exeshell\Open\command=system.exeshell=Explore

Downloads

The malware attempts to download files from:

  • http://aaszxt.ru/load4/[...].php?v=1&rs=%VolumeSerialNumber%&n=1&uid=1

Note: %VolumeSerialNumber% is volume serial number that the operating system assigns when a hard disk is formatted.

Stealth

For its stealth routine, it injects malicious code into the one of the following normal process:

  • svchost.exe
  • %program%

Note: %program% is usually "C:\Program Files\Internet Explorer\IEXPLORE.EXE -nohome" which was taken under the registry key "HKEY_CLASSES_ROOT\http\shell\open\command, (Default)".It also removes the hooked addresses corresponding to various NT Functions implemented in Ntoskrnl.exe, then restores them to their original values.

The malware will attempt to make the changes by exploiting the GDI Local Elevation of Privilege Vulnerability (CVE-2006-5758), which in unpatched machines allows a remote attacker to gain direct access to the kernel. If this method fails, it drops and executes a special driver that restores the pointers:

  • NtProtectVirtualMemory
  • NtOpenThread
  • NtTerminateThread
  • NtCreatePort
  • NtConnectPort
  • NtCreateKey
  • NtAdjustPrivilegesToken
  • NtCreateFile
  • NtWriteVirtualMemory
  • NtOpenProcess
  • NtCreateProcess
  • NtCreateProcessEx
  • NtCreateSection
  • NtCreateThread
  • NtDeleteKey
  • NtDeleteValueKey
  • NtDuplicateObject
  • NtEnumerateKey
  • NtEnumerateValueKey
  • NtLoadDriver
  • NtLoadKey
  • NtLoadKey2
  • NtNotifyChangeKey
  • NtOpenFile
  • NtOpenKey
  • NtOpenSection
  • NtQueryKey
  • NtQueryMultipleValueKey
  • NtQueryValueKey
  • NtReplaceKey
  • NtRestoreKey
  • NtResumeThread
  • NtSaveKey
  • NtSetContextThread
  • NtSetInformationFile
  • NtSetInformationKey
  • NtSetSystemInformation
  • NtSetValueKey
  • NtSuspendThread
  • NtSystemDebugControl
  • NtTerminateProcess

The malware creates and executes a kernel service driver as either of the following:

  • %systemdir%\Drivers\%servicename%.sys
  • %service_path_and_filename%

Both these files are detected as Rootkit:W32/Agent.UG.

It will query all services under the following registry entries, to obtain the %service_path_and_filename% and %servicename% of services that have:

  • Service Type = SERVICE_KERNEL_DRIVER and Start= SERVICE_DEMAND_START:
  • HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\%servicename%

It also creates the following registry entries to bypass the Windows Firewall:

  • HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\SharedAccess\Parameters\FirewallPolicy\StandardProfile\AuthorizedApplications\List{malware_executed_path_and_filename} = "{malware_executed_path_and_filename}:*:Enabled:EMOTIONS_EXECUTABLE"

Additionally, it creates a window with Classnames= "WNDCLASSXEMORES".






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