WORM_COREFLOOD.A

Puede haberlo descargado inadvertidamente un usuario mientras visitaba sitios Web maliciosos.

Detalles de entrada

Puede haberlo descargado inadvertidamente un usuario mientras visitaba sitios Web maliciosos.

Puede haberse descargado desde los sitios remotos siguientes:

• http://savupdate.{BLOCKED}evalidate.net/ctfup32.rar
• http://health.{BLOCKED}plus.net/ctfup32.rar

Instalación

Infiltra los archivos siguientes:

• %User Temp%\~~{random number}.tmp - also detected as BKDR_OFICLA.AI
• %System%\{random file name}.dat - encrypted data
• %System%\{random file name}.ocx - copy of itself

(Nota: %User Temp% es la carpeta Temp del usuario activo, que en el caso de Windows 2000, XP y Server 2003 suele estar en C:\Documents and Settings\{nombre de usuario}\Local Settings\Temp).

Técnica de inicio automático

Agrega las siguientes entradas de registro para permitir su ejecución automática cada vez que se inicia el sistema:

HKEY_CLASSES_ROOT\CLSID\{random CLSID}
(Default) = {random registry value}

HKEY_CLASSES_ROOT\CLSID\{random CLSID}\
InprocServer32
(Default) = %System%\{random file name}.ocx

HKEY_CLASSES_ROOT\CLSID\{random CLSID}\
InprocServer32
ThreadingModel = Apartment

HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\
Windows\CurrentVersion\Explorer\
ShellIconOverlayIdentifiers\{random key}
(Default) = {random CLSID}

Otros detalles

Según el análisis de los códigos, tiene las siguientes capacidades:

• Backdoor Routines

  Upon execution, it terminates EXPLORER.EXE and restarts the process with its code injected in it. It then attempts to resolve the host to any of the following servers:

  • http://{BLOCKED}ate.licensevalidate.net
  • http://{BLOCKED}s.hostfarmville.net

  Once a user opens a browser, it will perform a HTTP POST request with the following parameters containing system information:

  • http://{malware server}/index.php/r={parameter}&i=&v={version}&os={operating system}&s=&h=&d={parameter}&b={parameter}&u={parameter}&k={parameter}&m={parameter}&panic={parameter}&ie={parameter}&input={parameter}&c={country of affected system}&l={parameter}

  It will then expect to receive backdoor commands from the server.

  As of writing, the server replies with commands that does the following:

  • Assign a unique ID for the bot
  • Move a file named "c:\myservice.log" - not present in the system
  • Download, execute, and save the file downloaded from the website http://savupdate.{BLOCKED}evalidate.net/login.php as %User Temp%\tmsfoload.exe. Trend Micro detects this executable file as WORM_COREFLOOD.A. As of writing, the downloaded file is an updated copy of itself.

• Propagation via Network Shares

  • It scans the network for random IP addresses to search for target systems.
  • It then attempts to drop and execute the following copy of itself to target IP addresses:
  • %Windows%\System\ctfmnt.exe

• Download Routine

  It downloads a non-malicious component file named rar.exe from its server. It will then use this downloaded file to unpack the next file it will download from the server, ctfup32.rar, which is an archive file containing an updated copy of the malware.

  Initially, the malware will save all the downloaded files to the %User Temp% folder. Afterwards, it will install the contents of the archive ctfup32.rar to the %Windows%\System folder.

• Information Theft

  It monitors certain applications such as the following:

  • Firefox
  • Opera
  • Skype

  It logs user keystrokes when affected users visit Web sites with the following strings:

  • answer
  • challenge
  • clave
  • codigo
  • firma
  • identifica
  • memorable
  • parol
  • passphras
  • password
  • secret
  • secur
  • segur

• Other Details

• It logs the status of its installation to the affected system and to all the network shares it tried to infect to the following files:
• %User Temp%\tlmlg1.log
• %User Temp%\tlmlg2.log
• It uploads the file %User Temp%\cmtemp.tmp to its server.
• It may also perform the following:
  • Steal data from HTTPS sessions.
  • Read these component files, which are currently not found on systems: ie.dat, input.dat, other.dat, panic.dat.