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Threat Encyclopedia

TROJ_BAGLE.BI


ALIASES:

TrojanDownloader:Win32/Bagle.BU (Microsoft); W32/Bagle.dldr.gen (McAfee); Trojan.Tooso.L (Symantec); Email-Worm.Win32.Bagle.ck (Kaspersky); Trojan.Win32.Generic!BT (Sunbelt); Win32.Bagle.CJ@mm (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 modifies files, disabling programs and applications from properly running.

TECHNICAL DETAILS

File Size:

36,352 bytes

File Type:

EXE

Memory Resident:

Yes

Initial Samples Received Date:

04 Jan 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.

Installation

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

  • %System%\winshost.exe

(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.)

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
winshost.exe = "%System%\winshost.exe"

HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\
Windows\CurrentVersion\Run
winshost.exe = "%System%\winshost.exe"

Other System Modifications

This Trojan modifies the following files:

  • %System%\drivers\etc\hosts

(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.)

It adds the following registry keys:

HKEY_CURRENT_USER\Software\FirstRun

It adds the following registry entries:

HKEY_CURRENT_USER\Software\FirstRun
FirstRunRR = 1

Dropping Routine

This Trojan drops the following files:

  • %System%\wiwshost.exe

(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
    • FirstRun

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
    • winshost.exe="%System%\winshost.exe"
  • In HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion\Run
    • winshost.exe="%System%\winshost.exe"
  • In HKEY_CURRENT_USER\Software\FirstRun
    • FirstRunRR=1

Step 5

Search and delete this file

[ 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%\wiwshost.exe

Step 6

Restart in normal mode and scan your computer with your Trend Micro product for files detected as TROJ_BAGLE.BI. 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 deleted/modified files and/or registry entries from backup

*Note: Only Microsoft-related files/keys/values will be restored. If this malware/grayware also deleted registry keys/values related to programs that are not from Microsoft, please reinstall those programs on your computer.

    %System%\drivers\etc\hosts


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