Modified by: Mark Joseph Manahan
ALIASES:

Virus:Win32/Quervar.gen!B (Microsoft); W32/XDocCrypt.a (McAfee); Virus.Win32.Quervar.d (v) (Sunbelt)

 PLATFORM:

Windows 2000, Windows XP, Windows Server 2003

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

  • Threat Type: File infector

  • Destructiveness: No

  • Encrypted: Yes

  • In the wild: Yes

  OVERVIEW

Infection Channel: Infects files, Downloaded from the Internet, Dropped by other malware

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.

It prepends its codes to target files. It creates an infection marker in infected files.

It connects to certain URLs. It may do this to remotely inform a malicious user of its installation. It may also do this to download possibly malicious files onto the computer, which puts the computer at a greater risk of infection by other threats.

  TECHNICAL DETAILS

File Size: Varies
File Type: EXE
Memory Resident: No
Initial Samples Received Date: 16 Oct 2012
Payload: Connects to URLs/IPs

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 files:

  • %User Profile%\Application Data\{Random Folder}\{Random File name}.EXE.LNK
  • %User Profile%\Application Data\{Random Folder}\{Random File name}.EXE.INI
  • {Malware Path and File name}.{extension of the original file} - normal file that has been previously infected by PE_QUERVAR.E-0

(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.)

It drops and executes the following files:

  • %User Profile%\Application Data\{random folder name}\{random file name}.exe - detected as PE_QUERVAR.E-O

(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.)

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.)

It injects codes into the following process(es):

  • csrss.exe

Autostart Technique

This file infector adds the following registry entries to enable its automatic execution at every system startup:

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

File Infection

This file infector infects the following file types:

  • .exe
  • .doc
  • .docx
  • .xls
  • .xlsx

It prepends its codes to target files.

It creates an infection marker in infected files.

Process Termination

This file infector terminates the following processes if found running in the affected system's memory:

  • taskmgr.exe

Download Routine

This file infector connects to the following malicious URLs:

  • http://{BLOCKED}l.ru/33797470/2a06754.50664748/3052832ace10d474336096b36fbd49f05f190.exe?{random characters}
  • http://{BLOCKED}0.com/c/osnovnoj2.exe?{random number}
  • http://{BLOCKED}ewidea1.ru/1.php?{random characters}&pin={random characters}&crc={random characters}
  • http://www.{BLOCKED}oservisi.com/test/php/way.php?{random characters}&pin=58252D00982BC1DA&crc={random characters}

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

  SOLUTION

Minimum Scan Engine: 9.200
FIRST VSAPI PATTERN FILE: 9.464.04
FIRST VSAPI PATTERN DATE: 16 Oct 2012
VSAPI OPR PATTERN File: 9.465.00
VSAPI OPR PATTERN Date: 17 Oct 2012

Step 1

Before doing any scans, Windows XP, Windows Vista, and Windows 7 users must disable System Restore to allow full scanning of their computers.

Step 2

Remove the malware/grayware file that dropped/downloaded PE_QUERVAR.E

Step 3

Scan your computer with your Trend Micro product and note files detected as PE_QUERVAR.E

Step 4

Delete this registry value

[ Learn More ]

Important: Editing the Windows Registry incorrectly can lead to irreversible system malfunction. Please do this step only if you know how or you can ask assistance from your system administrator. Else, check this Microsoft article first before modifying your computer's registry.

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

Step 5

Search and delete these folders

[ Learn More ]
Please make sure you check the Search Hidden Files and Folders checkbox in the More advanced options option to include all hidden folders in the search result.
  • %User Profile%\Application Data\{random folder name}

Step 6

Scan your computer with your Trend Micro product to delete files detected as PE_QUERVAR.E. If the detected files have already been cleaned, deleted, or quarantined by your Trend Micro product, no further step is required. You may opt to simply delete the quarantined files. Please check this Knowledge Base page for more information.


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