ALIASES:

TrojanDownloader:Win32/Dofoil.L (Microsoft); Generic Downloader.ix (McAfee); Trojan.Smoaler (Symantec); Backdoor.Win32.Buterat.cvg (Kaspersky); Trojan.Win32.Generic!BT (Sunbelt); Trojan:W32/Yakes.BK (FSecure)

 PLATFORM:

Windows 2000, Windows XP, Windows Server 2003

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

  • Threat Type: Trojan

  • Destructiveness: No

  • Encrypted:

  • In the wild: Yes

  OVERVIEW

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

It disables Task Manager, Registry Editor, and Folder Options.

  TECHNICAL DETAILS

File Size: 38,912 bytes
File Type: EXE
Memory Resident: Yes
Initial Samples Received Date: 29 Nov 2011

Arrival Details

This Trojan 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 Trojan drops the following copies of itself into the affected system:

  • %User Profile%\Application Data\csrss.exe

(Note: %User Profile% is the current user's profile folder, which is usually C:\Windows\Profiles\{user name} on Windows 98 and ME, C:\WINNT\Profiles\{user name} on Windows NT, and C:\Documents and Settings\{user name} on Windows 2000, XP, and Server 2003.)

It creates the following folders:

  • %User Profile%\Protect\
  • %User Profile%\Application Data\Joudna
  • %User Profile%\Application Data\Hipui

(Note: %User Profile% is the current user's profile folder, which is usually C:\Windows\Profiles\{user name} on Windows 98 and ME, C:\WINNT\Profiles\{user name} on Windows NT, and C:\Documents and Settings\{user name} on Windows 2000, XP, and Server 2003.)

Autostart Technique

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

HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\
Windows\CurrentVersion\Run
rvotokh = "rundll32 %User Profile%\Protect\aysn.kq, rwvc"

HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\
Windows\CurrentVersion\Run
dxrdweq = "rundll32 %User Profile%\Protect\qmmrlpg.hf, tqda"

Other System Modifications

This Trojan deletes the following files:

  • %User Profile%\Application Data\csrss.exe
  • %User Profile%\Application Data\csrss.exe:Zone.Identifier
  • %User Temp%\1.tmp
  • %User Temp%\2.tmp
  • %User Temp%\3.tmp
  • %User Temp%\4.tmp
  • %User Temp%\5.tmp
  • %User Temp%\6.tmp
  • %User Temp%\7.tmp
  • %User Temp%\8.tmp
  • %User Temp%\9.tmp
  • %User Temp%\A.tmp
  • %User Profile%\Protect\gs32.txt
  • %User Profile%\Protect\f32.txt

(Note: %User Profile% is the current user's profile folder, which is usually C:\Windows\Profiles\{user name} on Windows 98 and ME, C:\WINNT\Profiles\{user name} on Windows NT, and C:\Documents and Settings\{user name} on Windows 2000, XP, and Server 2003.. %User Temp% is the current user's Temp folder, which is usually C:\Documents and Settings\{user name}\Local Settings\Temp on Windows 2000, XP, and Server 2003.)

It adds the following registry keys:

HKEY_CURRENT_USER\Software\Microsoft\
Windows\CurrentVersion\Policies\
Explorer\Run

HKEY_LOCAL_MACHINE\Software\Microsoft\
Sft

HKEY_CURRENT_USER\Software\paofjnog

HKEY_LOCAL_MACHINE\Software\paofjnog

HKEY_LOCAL_MACHINE\Software\Microsoft\
Windows\CurrentVersion\Policies\
Explorer\Run

HKEY_CURRENT_USER\Software\Microsoft\
Lytuc

It adds the following registry entries:

HKEY_CURRENT_USER\Software\paofjnog
knhtbiximc = {random values}

HKEY_LOCAL_MACHINE\SOFTWARE\paofjnog
knhtbiximc = {random values}

HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\
Windows\CurrentVersion\policies\
Explorer\Run
dwbgatldpz = "%System%\mpeg2data1.exe"

HKEY_CURRENT_USER\Software\Microsoft\
Windows\CurrentVersion\Internet Settings
6 = {random values}

HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\
Windows\CurrentVersion\Internet Settings
6 = {random values}

HKEY_CURRENT_USER\Software\Microsoft\
Lytuc
338ih93g = {random values}

It creates the following registry entry(ies) to disable Task Manager, Registry Tools and Folder Options:

HKEY_CURRENT_USER\Software\Microsoft\
Windows\CurrentVersion\Policies\
Explorer\Run
Microsoft = "%User Profile%\Application Data\csrss.exe"

Dropping Routine

This Trojan drops the following files:

  • %User Profile%\Protect\aysn.kq
  • %User Profile%\Protect\s32.txt
  • %System%\mpeg2data1.exe
  • %User Profile%\Joudna\heqoc.exe
  • %User Profile%\Hipui\ekek.taw
  • %User Profile%\Protect\qmmrlpg.hf

(Note: %User Profile% is the current user's profile folder, which is usually C:\Windows\Profiles\{user name} on Windows 98 and ME, C:\WINNT\Profiles\{user name} on Windows NT, and C:\Documents and Settings\{user name} on Windows 2000, XP, and Server 2003.. %System% is the Windows system folder, which is usually C:\Windows\System on Windows 98 and ME, C:\WINNT\System32 on Windows NT and 2000, or C:\Windows\System32 on Windows XP and Server 2003.)

Other Details

This Trojan connects to the following possibly malicious URL:

  • http://{BLOCKED}nsgroup.ru/true/index.php?{random characters}
  • http://{BLOCKED}tfriendly.com/html/license_43EC922A3D0E1F403834ED436BA90C5A686E6068E0C68C474C4DBA2C92504F636C070A0F9089CD55FF91CCEA4A8B02986223EFC24040056312ECEA8A1C5A813E699933730AD962103ABC2187FE25C718A5AE8335BCB38CA104474E71EF1FEBE0840A67DB21DF97DE3904E852B14EDB17AE7D00E75ACB63B4CE
  • http://{BLOCKED}tfriendly.com/html/license_43EC922A3D0E1F403834ED436BA90C5A686E6068E0C68C474C4DBA2C92504F636C070A0F9089CD55FF91CCEA4A8B02986223EFC24040056312ECEA8A1C5A813E699933730AD962103AEC74DEFA25C718AAFBD435BCB38CA104474E71EF1FEBE0840A67DB21DF97DE3904E852B14EDB17AE7D00E75ACB63B4CE

This report is generated via an automated analysis system.

  SOLUTION

Minimum Scan Engine: 9.200

Step 1

For Windows XP and Windows Server 2003 users, before doing any scans, please make sure you disable System Restore to allow full scanning of your computer.

Step 2

Restart in Safe Mode

[ Learn More ]

Step 3

Enable Registry Editor, Task Manager, and Folder options

[ Learn More ]
By doing this step, you also enable other applications/programs disabled by this malware/grayware.

Step 4

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_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\Policies\Explorer
    • Run
  • In HKEY_LOCAL_MACHINE\Software\Microsoft
    • Sft
  • In HKEY_CURRENT_USER\Software
    • paofjnog
  • In HKEY_LOCAL_MACHINE\Software
    • paofjnog
  • In HKEY_LOCAL_MACHINE\Software\Microsoft\Windows\CurrentVersion\Policies\Explorer
    • Run
  • In HKEY_CURRENT_USER\Software\Microsoft
    • Lytuc

Step 5

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\CurrentVersion\Run
    • rvotokh="rundll32 %User Profile%\Protect\aysn.kq, rwvc"
  • In HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion\Run
    • dxrdweq="rundll32 %User Profile%\Protect\qmmrlpg.hf, tqda"
  • In HKEY_CURRENT_USER\Software\paofjnog
    • knhtbiximc={random values}
  • In HKEY_LOCAL_MACHINE\SOFTWARE\paofjnog
    • knhtbiximc={random values}
  • In HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion\policies\Explorer\Run
    • dwbgatldpz="%System%\mpeg2data1.exe"
  • In HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\Internet Settings
    • 6={random values}
  • In HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion\Internet Settings
    • 6={random values}
  • In HKEY_CURRENT_USER\Software\Microsoft\Lytuc
    • 338ih93g={random values}

Step 6

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%\Protect\
  • %User Profile%\Application Data\Joudna
  • %User Profile%\Application Data\Hipui

Step 7

Search and delete these files

[ Learn More ]
There may be some component 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 Profile%\Protect\aysn.kq
  • %User Profile%\Protect\s32.txt
  • %System%\mpeg2data1.exe
  • %User Profile%\Joudna\heqoc.exe
  • %User Profile%\Hipui\ekek.taw
  • %User Profile%\Protect\qmmrlpg.hf

Step 8

Restart in normal mode and scan your computer with your Trend Micro product for files detected as TROJ_BREDO.CNI. 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.

Step 9

Restore this file from backup only Microsoft-related files will be restored. If this malware/grayware also deleted files related to programs that are not from Microsoft, please reinstall those programs on you computer again.

  • %User Profile%\Application Data\csrss.exe
  • %User Profile%\Application Data\csrss.exe:Zone.Identifier
  • %User Temp%\1.tmp
  • %User Temp%\2.tmp
  • %User Temp%\3.tmp
  • %User Temp%\4.tmp
  • %User Temp%\5.tmp
  • %User Temp%\6.tmp
  • %User Temp%\7.tmp
  • %User Temp%\8.tmp
  • %User Temp%\9.tmp
  • %User Temp%\A.tmp
  • %User Profile%\Protect\gs32.txt
  • %User Profile%\Protect\f32.txt


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