Analysis by: Jennifer Gumban
 Modified by: Nikko Tamana
ALIASES:

a variant of Win32/Floxif.E (ESET-NOD32), W32/Fixflo.A.gen!Eldorado (FProt), W32/Floxif.E (Fortinet), Win32.Virus.Floxif.Chl (Tencent)

 PLATFORM:

Windows

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

  • Threat Type: File infector

  • Destructiveness: No

  • Encrypted: Yes

  • 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.

It appends its codes to target files. It infects certain file types by inserting code in the said files.

As of this writing, the said sites are inaccessible.

  TECHNICAL DETAILS

File Size: 74007 bytes
File Type: DLL
Memory Resident: Yes
Initial Samples Received Date: 03 Sep 2014

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 Temp%\{random file name}.sys - component used to delete running processes
  • {Drive letter}:\­pagefile.pif
  • {Drive letter}:\­autorun.inf

(Note: %User Temp% is the user's temporary folder, where it usually is C:\Documents and Settings\{user name}\Local Settings\Temp on Windows 2000, Windows Server 2003, and Windows XP (32- and 64-bit); C:\Users\{user name}\AppData\Local\Temp on Windows Vista (32- and 64-bit), Windows 7 (32- and 64-bit), Windows 8 (32- and 64-bit), Windows 8.1 (32- and 64-bit), Windows Server 2008, and Windows Server 2012.)

Autostart Technique

This File infector modifies the following registry entry(ies) to enable its automatic execution at every system startup:

HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\
Windows NT\CurrentVersion\Windows
AppInit_DLLs = "{malware file path and file name}.dll"

It adds and runs the following services:

  • Service Name: KILLPRC
  • Display Name: KILLPRC
  • Start Type: SERVICE_DEMAND_START
  • Binary Pathname: "%User Temp%\{random file name}.sys"

(Note: %User Temp% is the user's temporary folder, where it usually is C:\Documents and Settings\{user name}\Local Settings\Temp on Windows 2000, Windows Server 2003, and Windows XP (32- and 64-bit); C:\Users\{user name}\AppData\Local\Temp on Windows Vista (32- and 64-bit), Windows 7 (32- and 64-bit), Windows 8 (32- and 64-bit), Windows 8.1 (32- and 64-bit), Windows Server 2008, and Windows Server 2012.)

Other System Modifications

This File infector adds the following registry entries as part of its installation routine:

HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\
Windows NT\CurrentVersion\Windows
RequireSignedAppInit_DLLs = 0

It modifies the following registry entries:

HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\
Windows NT\CurrentVersion\Windows
LoadAppInit_DLLs = 1

(Note: The default value data of the said registry entry is 0.)

File Infection

This File infector appends its codes to target files.

It infects files with the following file extensions by inserting code in the said files:

  • EXE
  • DLL

It avoids infecting folders containing the following strings:

  • %Windows% and subfolders
  • {CD Drive Letter}

(Note: %Windows% is the Windows folder, where it usually is C:\Windows on all Windows operating system versions.)

Download Routine

This File infector connects to the following website(s) to download and execute a malicious file:

  • http://www.ai{BLOCKED}.com/setup.exe
  • http://www.5is{BLOCKED}.com/setup.exe

As of this writing, the said sites are inaccessible.

Other Details

This File infector connects to the following URL(s) to check for an Internet connection:

  • www.baidu.com

NOTES:

It infects the files of running processes.

It creates the following temporary files and deletes them afterwards as part of its infection routine:

  • {original file name}.{original file extension}.tmp
  • {original file name}.{original file extension}.dat
It checks for the presence of antivirus and security applications. When found, its sleeps for infinite time. Therefore, the malware will not perform its intended routines.

  SOLUTION

Minimum Scan Engine: 9.850
FIRST VSAPI PATTERN FILE: 11.126.05
FIRST VSAPI PATTERN DATE: 03 Sep 2014
VSAPI OPR PATTERN File: 11.127.00
VSAPI OPR PATTERN Date: 04 Sep 2014

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

Note that not all files, folders, and registry keys and entries are installed on your computer during this malware's/spyware's/grayware's execution. This may be due to incomplete installation or other operating system conditions. If you do not find the same files/folders/registry information, please proceed to the next step.

Step 3

Scan your computer with your Trend Micro product and note files detected as PE_FLOXIF.SM-O

Step 4

Restart in Safe Mode

[ Learn More ]

Step 5

Disable this malware service

[ Learn More ]
  • Service Name: KILLPRC

Step 6

Search and delete this file

[ Learn More ]
There may be some files that are hidden. Please make sure you check the Search Hidden Files and Folders checkbox in the "More advanced options" option to include all hidden files and folders in the search result.
  • %User Temp%\{random file name}.sys - use ImagePath in KILLRPC service as basis
  • {Drive letter}:\pagefile.pif
  • {Drive letter}:\autorun.inf

Step 7

Delete this registry key

[ 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_LOCAL_MACHINE\SYSTEM\ControlSet001\services
    • KILLPRC

Step 8

Restore these modified registry values

[ Learn More ]

Important:Editing the Windows Registry incorrectly can lead to irreversible system malfunction. Please do this only if you know how to or you can seek your system administrator's help. You may also check out this Microsoft article first before modifying your computer's registry.

  • In HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows NT\CurrentVersion\Windows
    • From: LoadAppInit_DLLs = 1
      To: LoadAppInit_DLLs = 0
  • In HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows NT\CurrentVersion\Windows
    • From: AppInit_DLLs = "{malware file path and file name}.dll"
      To: AppInit_DLLs = ""

Step 9

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_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows NT\CurrentVersion\Windows
    • RequireSignedAppInit_DLLs = 0

Step 10

Restart in normal mode and scan your computer with your Trend Micro product for files detected as PE_FLOXIF.SM-O. 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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