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TROJ_DROPPER.IUR

October 09, 2012
 Analysis by: Abraham Latimer Camba
 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 connects to certain URLs. It may do this to remotely inform a malicious user of its installation. It may also do this to download possibly malicious files onto the computer, which puts the computer at a greater risk of infection by other threats.

It deletes the initially executed copy of itself.

  TECHNICAL DETAILS

File Size:

106,496 bytes

File Type:

EXE

Memory Resident:

Yes

Initial Samples Received Date:

21 Mar 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%\{random filename}.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.)

It adds the following mutexes to ensure that only one of its copies runs at any one time:

  • 6A57BEED

It injects itself into the following processes as part of its memory residency routine:

  • csrss.exe

Autostart Technique

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

HKEY_LOCAL_MACHINE\Software\Microsoft\
Windows NT\CurrentVersion\Image File Execution Options\
userinit.exe
Debugger = "%System%\{random file name}.exe"

Other System Modifications

This Trojan modifies the following registry key(s)/entry(ies) as part of its installation routine:

HKEY_USERS\.DEFAULT\Software\
Microsoft\Windows\CurrentVersion\
Explorer\Shell Folders
Cookies = "%System%\config\systemprofile\Cookies"

(Note: The default value data of the said registry entry is C:\Documents and Settings\NetworkService\Cookies.)

HKEY_USERS\.DEFAULT\Software\
Microsoft\Windows\CurrentVersion\
Explorer\Shell Folders
Cache = "%System%\config\systemprofile\Local Settings\Temporary Internet Files"

(Note: The default value data of the said registry entry is C:\Documents and Settings\NetworkService\Local Settings\Temporary Internet Files.)

HKEY_USERS\.DEFAULT\Software\
Microsoft\Windows\CurrentVersion\
Explorer\Shell Folders
History = "%System%\config\systemprofile\Local Settings\History"

(Note: The default value data of the said registry entry is C:\Documents and Settings\NetworkService\Local Settings\History.)

HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\
Windows\CurrentVersion\Internet Settings\
Cache\Paths
Directory = "%System%\config\systemprofile\Local Settings\Temporary Internet Files\Content.IE5"

(Note: The default value data of the said registry entry is %Temporary Internet Files%\Content.IE5.)

HKEY_CURRENT_USER\Software\Microsoft\
Windows\CurrentVersion\Internet Settings\
Zones\3
1609 = "0"

(Note: The default value data of the said registry entry is 1.)

HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\
Windows\CurrentVersion\Internet Settings\
Cache\Paths\path1
CachePath = "%System%\config\systemprofile\Local Settings\Temporary Internet Files\Content.IE5\Cache1"

(Note: The default value data of the said registry entry is %Temporary Internet Files%\Content.IE5\Cache1.)

HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\
Windows\CurrentVersion\Internet Settings\
Cache\Paths\path2
CachePath = "%System%\config\systemprofile\Local Settings\Temporary Internet Files\Content.IE5\Cache2"

(Note: The default value data of the said registry entry is %Temporary Internet Files%\Content.IE5\Cache2.)

HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\
Windows\CurrentVersion\Internet Settings\
Cache\Paths\path3
CachePath = "%System%\config\systemprofile\Local Settings\Temporary Internet Files\Content.IE5\Cache3"

(Note: The default value data of the said registry entry is %Temporary Internet Files%\Content.IE5\Cache3.)

HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\
Windows\CurrentVersion\Internet Settings\
Cache\Paths\path4
CachePath = "%System%\config\systemprofile\Local Settings\Temporary Internet Files\Content.IE5\Cache4"

(Note: The default value data of the said registry entry is %Temporary Internet Files%\Content.IE5\Cache4.)

It adds the following registry keys as part of its installation routine:

HKEY_LOCAL_MACHINE\Software\Microsoft\
Windows\CurrentVersion\Internet Settings\
5.0\203E7401

HKEY_LOCAL_MACHINE\Software\Microsoft\
Windows NT\CurrentVersion\Image File Execution Options\
userinit.exe

It also creates the following registry entry(ies) as part of its installation routine:

HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\
Windows\CurrentVersion\Internet Settings\
5.0\203E7401
@ = "{hex values}"

HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\
Windows\CurrentVersion\Internet Settings\
5.0\203E7401
B5C9 = "0"

HKEY_USERS\.DEFAULT\Software\
Microsoft\Windows\CurrentVersion\
Internet Settings
GlobalUserOffline = "0"

HKEY_USERS\.DEFAULT\Software\
Microsoft\Windows\CurrentVersion\
Internet Settings\Connections
DefaultConnectionSettings = "{hex values}"

Download Routine

This Trojan connects to the following malicious URLs:

  • {BLOCKED}ime.net
  • {BLOCKED}ime.net/was/vas.php

Other Details

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

  • http://google.com

It deletes the initially executed copy of itself

  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

Scan your computer with your Trend Micro product and note files detected as TROJ_DROPPER.IUR

Step 3

Restart in Safe Mode

[ Learn More ]

Step 4

Delete these 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_USERS\.DEFAULT\Software\Microsoft\Windows\CurrentVersion\Internet Settings
    • GlobalUserOffline = "0"
  • In HKEY_USERS\.DEFAULT\Software\Microsoft\Windows\CurrentVersion\Internet Settings\Connections
    • DefaultConnectionSettings = "{hex values}"

Step 6

Restore this modified registry value

[ 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_USERS\.DEFAULT\Software\Microsoft\Windows\CurrentVersion\Explorer\Shell Folders
    • From: Cookies = "%System%\config\systemprofile\Cookies"
      To: Cookies = C:\Documents and Settings\NetworkService\Cookies
  • In HKEY_USERS\.DEFAULT\Software\Microsoft\Windows\CurrentVersion\Explorer\Shell Folders
    • From: Cache = "%System%\config\systemprofile\Local Settings\Temporary Internet Files"
      To: Cache = C:\Documents and Settings\NetworkService\Local Settings\Temporary Internet Files
  • In HKEY_USERS\.DEFAULT\Software\Microsoft\Windows\CurrentVersion\Explorer\Shell Folders
    • From: History = "%System%\config\systemprofile\Local Settings\History"
      To: History = C:\Documents and Settings\NetworkService\Local Settings\History
  • In HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion\Internet Settings\Cache\Paths
    • From: Directory = "%System%\config\systemprofile\Local Settings\Temporary Internet Files\Content.IE5"
      To: Directory = %Temporary Internet Files%\Content.IE5
  • In HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\Internet Settings\Zones\3
    • From: 1609 = "0"
      To: 1609 = 1
  • In HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion\Internet Settings\Cache\Paths\path1
    • From: CachePath = "%System%\config\systemprofile\Local Settings\Temporary Internet Files\Content.IE5\Cache1"
      To: CachePath = %Temporary Internet Files%\Content.IE5\Cache1
  • In HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion\Internet Settings\Cache\Paths\path2
    • From: CachePath = "%System%\config\systemprofile\Local Settings\Temporary Internet Files\Content.IE5\Cache2"
      To: CachePath = %Temporary Internet Files%\Content.IE5\Cache2
  • In HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion\Internet Settings\Cache\Paths\path3
    • From: CachePath = "%System%\config\systemprofile\Local Settings\Temporary Internet Files\Content.IE5\Cache3"
      To: CachePath = %Temporary Internet Files%\Content.IE5\Cache3
  • In HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion\Internet Settings\Cache\Paths\path4
    • From: CachePath = "%System%\config\systemprofile\Local Settings\Temporary Internet Files\Content.IE5\Cache4"
      To: CachePath = %Temporary Internet Files%\Content.IE5\Cache4

Step 7

Search and delete the file detected as TROJ_DROPPER.IUR

*Note: Some component files may be 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.

To manually delete a malware/grayware file from the affected system:

  1. Right-click Start then click Search....
  2. In the Named input box, type the name of the file that was detected earlier.
  3. In the Look In drop-down list, select My Computer then press Enter.
  4. Once located, select the file then press SHIFT+DELETE to delete it.

Step 8

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