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PE_QUERVAR.F

October 09, 2013
 Modified by: Anthony Joe Melgarejo
 ALIASES:

Virus:Win32/Quervar.gen!B (Microsoft), Trojan.Exprez.B (Symantec), W32/Quervar-C (Sophos), Virus.Win32.Quervar.a (Sunbelt), W32/Quervar.A (F-Prot), WIN.Worm.Dorifel (ClamAV), Win32/Quervar.E virus (ESET), W32/Quervar.E!tr (Fortinet), Trojan-Dropper.Delf (Ikarus)

 PLATFORM:

Windows 2000, Windows XP, Windows Server 2003

 OVERALL RISK RATING:
 DAMAGE POTENTIAL:
 DISTRIBUTION POTENTIAL:
 REPORTED INFECTION:

  • Threat Type: File infector

  • Destructiveness: No

  • Encrypted:

  • In the wild: Yes

  OVERVIEW


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

  TECHNICAL DETAILS

File Size:

Varies

File Type:

EXE

Memory Resident:

No

Initial Samples Received Date:

17 Jan 2013

Arrival Details

This file infector 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 file infector drops the following copies of itself into the affected system:

  • %Application Data%\{random folder name}\{random file name}.exe

(Note: %Application Data% is the current user's Application Data folder, which is usually C:\Documents and Settings\{user name}\Application Data on Windows 2000, XP, and Server 2003, or C:\Users\{user name}\AppData\Roaming on Windows Vista and 7.)

It drops the following component file(s):

  • %Application Data%\{random folder name}\{random file name}.exe.lnk

(Note: %Application Data% is the current user's Application Data folder, which is usually C:\Documents and Settings\{user name}\Application Data on Windows 2000, XP, and Server 2003, or C:\Users\{user name}\AppData\Roaming on Windows Vista and 7.)

It creates the following folders:

  • %User Profile%\Application Data\{random folder name}

(Note: %User Profile% is the current user's profile folder, which is usually C:\Documents and Settings\{user name} on Windows 2000, XP, and Server 2003, or C:\Users\{user name} on Windows Vista and 7.)

Autostart Technique

This file infector modifies the following registry entries to ensure it automatic execution at every system startup:

HKEY_CURRENT_USER\Software\Microsoft\
Windows NT\CurrentVersion\Windows
load = "%Application Data%\{random folder name}\{random filename}.exe.lnk"

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

File Infection

This file infector infects the following file types:

  • exe
  • doc
  • docx
  • xls
  • xlsx

NOTES:

This file infector renames the extension of the infected file as follows:

  • .doc to .cod.scr
  • .docx to .xcod.scr
  • .xls to .slx.scr
  • .xlsx to .xslx.scr

It then deletes the original copy of the infected files.