Backdoor:W32/Bohu.A

Summary

This program installs various files onto the system. Among the components installed are: a backdoor which connects to an external site to optain updates and other settings; and a component that monitors web traffic to various search engines in China and the domains of certain antivirus (AV) vendors.

Disinfection & Removal

Allow F-Secure Anti-Virus to disinfect the relevant files.

For more general information on disinfection, please see Removal Instructions.

Technical Details

The malware is detected as Trojan-Dropper:W32/Bohu.A and is a NullSoft installer that contains the following:

• uuse-5905.exe
• %ProgramFiles%\baidu\dsop7.xml
• %ProgramFiles%\baidu\msfsg.exe

Besides installing the files, it also modify the system's IP settings to use DHCP.

UUSE-5905.EXE

This file is an installer of a media player application. This is a decoy installed by the malware to make users think they have installed a valid application.

MSFSG.EXE

This file is some sort of utility that is being used by the malware for its different routines.

This utility is able to do the following:

• append garbage data to the end of a file
• modify DNS settings
• compress and uncompress samples

This utility is detected as Trojan.Generic.4982818.

DSOP7.XML

This file is the compressed form of another Nullsoft installer which contains the malicious components of the malware. The installer (setup321046.exe) is extracted by the malware using the msfsg.exe utility.

SETUP321046.EXE contains the following:

• %ProgramFiles%\baidu\dsetup.exe
• %ProgramFiles%\baidu\mpflt.inf
• %ProgramFiles%\baidu\mpflt_m.inf
• %ProgramFiles%\baidu\msfsg.exe
• %ProgramFiles%\baidu\newnetgar.dll
• %ProgramFiles%\baidu\siglow.dll
• %ProgramFiles%\baidu\siglow.sys
• %ProgramFiles%\baidu\spass.dll
• %ProgramFiles%\baidu\SyssData.bin

After extracting the files, SETUP321046.EXE will use msfsg.exe to append garbage data to the following files:

• %ProgramFiles%\baidu\dsetup.exe
• %ProgramFiles%\baidu\newnetgar.dll
• %ProgramFiles%\baidu\siglow.dll
• %ProgramFiles%\baidu\siglow.sys
• %ProgramFiles%\baidu\spass.dll

Then it copies the following files:

• newnetgar.dll -> %System%\nethome32.dll
• spass.dll -> %System%\netplayone\netplayone.dll

SETUP321046.EXE will create the following registry entries/service:

• HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\WinSock2\speednet_sph PathName = %System%\netplayone\netplayone.dll
• HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\NetHomeIDE

SETUP321046.EXE will then launch DSETUP.EXE to install the following NDIS driver and notify object:

• siglow.sys -> %System%\drivers\siglow.sys
• siglow.dll -> %System%\drivers\siglow.dll

SETUP321046.EXE also attempts to change the DNS settings to 61.158.160.197 and 61.158.160.206 using the msfsg.exe utility.

NEWNETGAR.DLL / NETHOME32.DLL

This component contains routines that connects to http://[...].gogle.cn/ to obtain updates and other settings. It is detected as Backdoor:W32/Bohu.A.

SPASS.DLL / NETPLAYONE.DLL

This component monitors network traffic related to the following AV-related processes:

• safeboxtray.exe
• 360safebox.exe
• 360rp.exe
• 360safe.exe
• 360sd.exe
• dsmain.exe
• superkiller.exe

It modifies traffic made by these processes to the following addresses:

• qup.f.360.cn/file_health_info.php
• up.f.360.cn/upload.php

These addresses are related to AV cloud services. By doing this, the malware may disable cloud-based protection of the affected product.

This component also modifies traffic to several addresses related to the following domains:

• google.cn
• baidu.com
• sogou.com

It connects to the following for the settings:

• http://[...].l0086.com.cn/Service.asmx
• http://[...].02l.cn/Service.asmx

This component is detected as Trojan:W32/Bohu.A.

SIGLOW.SYS / SIGLOW.DLL

These components are responsible for dropping network traffic to the following AV related sites:

• rsup10.rising.com.cn
• rsdownauto.rising.com.cn
• cloudinfo.rising.com.cn
• cu005.www.duba.net
• cu010.www.duba.net
• cu.www.duba.net
• f-sq.ijinshan.com
• geo.kaspersky.com
• stat.ijinshan.com
• qup.f.360.cn
• h.qup.f.360.cn
• up.f.360.cn
• down.360safe.com
• dl.360safe.com
• sdup.360.cn

These components are also detected as Trojan:W32/Bohu.A.