TROJ_DLOADR.USBD03AVC

October 12, 2012
 ALIASES:

TrojanDownloader:Win32/Fosniw.C (Microsoft); Trojan.Gen (Symantec); Trojan.Win32.Scar.eaiu (Kaspersky); Trojan-Downloader.Win32.Fosniw.c (v) (Sunbelt); Gen:Trojan.Heur.JP.pm0@aaqaf0mG (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.

  TECHNICAL DETAILS

File Size:

254,464 bytes

File Type:

EXE

Memory Resident:

Yes

Initial Samples Received Date:

23 Apr 2012

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.

Autostart Technique

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

HKEY_CURRENT_USER\Software\Microsoft\
Windows\CurrentVersion\Run
d8d4dac4c6c5da9fd4c9d4 = "%User Profile%\Application Data\uwtk.exe"

Other System Modifications

This Trojan deletes the following files:

  • %User Profile%\Application Data\uwtk.exe
  • %Windows%\fonts\msgothic.ttf
  • %Windows%\fonts\msuigoth.ttf
  • %Windows%\fonts\MSMINCHO.TTF
  • %Windows%\fonts\Gulim.ttf
  • %Windows%\fonts\Gulimche.ttf
  • %Windows%\fonts\Dotum.ttf
  • %Windows%\fonts\Batang.ttf
  • %Windows%\fonts\Gungsuh.ttf
  • %Windows%\fonts\Simsun.ttf
  • %Windows%\fonts\nsimsun.ttf
  • %Windows%\fonts\MingLiU.ttf
  • %Windows%\fonts\pmingliu.ttf
  • %System%\SET2.tmp
  • %System%\kbd101b.dll
  • %System%\SET4.tmp
  • %System%\kbd101c.dll
  • %System%\SET6.tmp
  • %System%\kbd103.dll
  • %System%\SET8.tmp
  • %System%\kbd106.dll
  • %System%\SETA.tmp
  • %System%\kbdjpn.dll
  • %System%\SETC.tmp
  • %System%\kbdkor.dll

(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.. %Windows% is the Windows folder, which is usually C:\Windows or C:\WINNT.. %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.)

It adds the following registry keys:

HKEY_CURRENT_USER\Software\a0f0f62ea1b1

HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\
Windows\CurrentVersion\Uninstall\
uwtk

HKEY_CURRENT_USER\Software\Microsoft\
Internet Explorer\International\CpMRU

It adds the following registry entries:

HKEY_CURRENT_USER\Software\a0f0f62ea1b1
idt = "201204221727"

HKEY_CURRENT_USER\Software\a0f0f62ea1b1
ver = "1.0.0.6"

HKEY_CURRENT_USER\Software\a0f0f62ea1b1
Location = "d8d4dac4c6c5da9fd4c9d4"

HKEY_CURRENT_USER\Software\a0f0f62ea1b1
pid = "trb1"

HKEY_CURRENT_USER\Software\a0f0f62ea1b1
prj = "4"

HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\
Windows\CurrentVersion\Uninstall\
uwtk
DisplayName = "Windows IEK uwtk Uninstall"

HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\
Windows\CurrentVersion\Uninstall\
uwtk
UninstallString = "%User Profile%\Application Data\uwtk.exe uninstall"

HKEY_CURRENT_USER\Software\Microsoft\
Internet Explorer\International\CpMRU
Enable = "1"

HKEY_CURRENT_USER\Software\Microsoft\
Internet Explorer\International\CpMRU
Size = "a"

HKEY_CURRENT_USER\Software\Microsoft\
Internet Explorer\International\CpMRU
InitHits = "64"

HKEY_CURRENT_USER\Software\Microsoft\
Internet Explorer\International\CpMRU
Factor = "14"

HKEY_CURRENT_USER\Software\Microsoft\
Internet Explorer\International
W2KLpk = "1"

HKEY_CURRENT_USER\Software\Microsoft\
Internet Explorer\International
W2KLpk = "0"

Dropping Routine

This Trojan drops the following files:

  • %System%\SET1.tmp
  • %System%\SET3.tmp
  • %System%\SET5.tmp
  • %System%\SET7.tmp
  • %System%\SET9.tmp
  • %System%\SETB.tmp
  • %System%\SET2.tmp
  • %System%\SET4.tmp
  • %System%\SET6.tmp
  • %System%\SET8.tmp
  • %System%\SETA.tmp
  • %System%\SETC.tmp

(Note: %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.)

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

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
    • a0f0f62ea1b1
  • In HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion\Uninstall
    • uwtk
  • In HKEY_CURRENT_USER\Software\Microsoft\Internet Explorer\International
    • CpMRU

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\CurrentVersion\Run
    • d8d4dac4c6c5da9fd4c9d4 = "%User Profile%\Application Data\uwtk.exe"
  • In HKEY_CURRENT_USER\Software\a0f0f62ea1b1
    • idt = "201204221727"
  • In HKEY_CURRENT_USER\Software\a0f0f62ea1b1
    • ver = "1.0.0.6"
  • In HKEY_CURRENT_USER\Software\a0f0f62ea1b1
    • Location = "d8d4dac4c6c5da9fd4c9d4"
  • In HKEY_CURRENT_USER\Software\a0f0f62ea1b1
    • pid = "trb1"
  • In HKEY_CURRENT_USER\Software\a0f0f62ea1b1
    • prj = "4"
  • In HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion\Uninstall\uwtk
    • DisplayName = "Windows IEK uwtk Uninstall"
  • In HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion\Uninstall\uwtk
    • UninstallString = "%User Profile%\Application Data\uwtk.exe uninstall"
  • In HKEY_CURRENT_USER\Software\Microsoft\Internet Explorer\International\CpMRU
    • Enable = "1"
  • In HKEY_CURRENT_USER\Software\Microsoft\Internet Explorer\International\CpMRU
    • Size = "a"
  • In HKEY_CURRENT_USER\Software\Microsoft\Internet Explorer\International\CpMRU
    • InitHits = "64"
  • In HKEY_CURRENT_USER\Software\Microsoft\Internet Explorer\International\CpMRU
    • Factor = "14"
  • In HKEY_CURRENT_USER\Software\Microsoft\Internet Explorer\International
    • W2KLpk = "1"
  • In HKEY_CURRENT_USER\Software\Microsoft\Internet Explorer\International
    • W2KLpk = "0"

Step 5

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.
  • %System%\SET1.tmp
  • %System%\SET3.tmp
  • %System%\SET5.tmp
  • %System%\SET7.tmp
  • %System%\SET9.tmp
  • %System%\SETB.tmp
  • %System%\SET2.tmp
  • %System%\SET4.tmp
  • %System%\SET6.tmp
  • %System%\SET8.tmp
  • %System%\SETA.tmp
  • %System%\SETC.tmp

Step 6

Restart in normal mode and scan your computer with your Trend Micro product for files detected as TROJ_DLOADR.USBD03AVC. 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 7

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\uwtk.exe
  • %Windows%\fonts\msgothic.ttf
  • %Windows%\fonts\msuigoth.ttf
  • %Windows%\fonts\MSMINCHO.TTF
  • %Windows%\fonts\Gulim.ttf
  • %Windows%\fonts\Gulimche.ttf
  • %Windows%\fonts\Dotum.ttf
  • %Windows%\fonts\Batang.ttf
  • %Windows%\fonts\Gungsuh.ttf
  • %Windows%\fonts\Simsun.ttf
  • %Windows%\fonts\nsimsun.ttf
  • %Windows%\fonts\MingLiU.ttf
  • %Windows%\fonts\pmingliu.ttf
  • %System%\SET2.tmp
  • %System%\kbd101b.dll
  • %System%\SET4.tmp
  • %System%\kbd101c.dll
  • %System%\SET6.tmp
  • %System%\kbd103.dll
  • %System%\SET8.tmp
  • %System%\kbd106.dll
  • %System%\SETA.tmp
  • %System%\kbdjpn.dll
  • %System%\SETC.tmp
  • %System%\kbdkor.dll


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