Trojan:Win32/Nebular.gen!D is a trojan that gathers information from the affected machine and sends it to remote sites. It has been distributed as an executable file that is approximately 43,000 to 47,000 in size (depending on the small differences across minor variants).
Installation
When executed Trojan:Win32/Nebular.gen!D creates a mutex that consists of 4 ascii digits, for example "1006", or "3002" (this mutex differs across minor variants of the trojan). If the mutex already exists, the trojan terminates.
If the mutex does not already exist, the trojan drops the following files:
- %userprofiletemp%\twe[one random character].tmp
- %userprofiletemp%\twe[one random character].bat (same filename as used above, for example twec.tmp and twec.bat). This batch file is used to delete the .tmp file and itself.
- <system folder>\win[three random characters]32.dll file. (for example winjte32.dll)
Note - <system folder> and %userprofiletemp% refer to variable locations that are determined by the malware by querying the Operating System. The default installation location for the System folder for Windows 2000 and NT is C:\Winnt\System32; and for XP and Vista is C:\Windows\System32. Whereas %userprofiletemp% is normally located at %UserProfile%\Local Settings\Temp
The trojan also drops an additional batch file in the current directory to delete both its original executable and the batch file itself.
Trojan:Win32/Nebular.gen!D launches a hidden instance of iexplore and injects the dropped dll into the iexplore process space.
The trojan also modifies the following registry entry in order to run on every start up:
Adds value: "Asynchronous"
With data: "1"
To subkey: HKLM\SOFTWARE\Microsoft\Windows NT\CurrentVersion\Winlogon\Notify\<trojan DLL minus .dll extension>
It encodes and stores information for its own use in the following keys:
HKLM\SOFTWARE\Microsoft\MSSMGR\Data
HKLM\SOFTWARE\Microsoft\MSSMGR\LSTV
HKLM\SOFTWARE\Microsoft\MSSMGR\BSTV
HKLM\SOFTWARE\Microsoft\MSSMGR\PSTV
HKLM\SOFTWARE\Microsoft\MSSMGR\SSTV
HKLM\SOFTWARE\Microsoft\MSSMGR\SSLIST
The trojan also makes the following further modifications to the registry:
Adds value:"C:\Program Files\Internet Explorer\iexplore.exe"
With data: "internet explorer"
To subkey: HKCU\Software\Microsoft\Windows\ShellNoRoam\MUICache
Adds value:"NodeSlots"
With data: ""
To subkey:HKCU\Software\Microsoft\Windows\ShellNoRoam\BagMRU
Adds value:"Locked"
With data: "1"
To subkey: HKCU\Software\Microsoft\Internet Explorer\Toolbar
Adds value:"Order"
With data: "."
To subkey: HKCU\Software\Microsoft\Windows\CurrentVersion\Explorer\MenuOrder\Favorites\Links
Using the dropped DLL, the trojan creates the mutex 'm3d5rt10' to avoid running multiple copies of itself in memory.
Payload
Collects Information
Trojan:Win32/Nebular.gen!D collects hardware information from the affected machine and sends it to the following sites:
- smart-security.biz
- searchmeup.biz
Collected information may include the affected machine's Media Access Control (MAC) address, Volume Serial Number, Brand, Version and a Unique ID of an RAS capable device, (which would normally be a modem).
The trojan is also able to update itself through from the URLs listed above.
Analysis by Oleg Petrovsky
