PE_RAMNIT.DEN-O

 Analysis by: kathleenno

 PLATFORM:

Windows 2000, Windows XP, Windows Server 2003

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

  • Threat Type: File infector

  • Destructiveness: No

  • Encrypted: No

  • In the wild: Yes

  OVERVIEW

Infection Channel:

Propagates via removable drives


This file infector opens a hidden instance of IEXPLORE.EXE and connects to remote sites to download and execute possible malicious file(s).

Infected files are detected as follows:

  • DLL and EXE files - PE_RAMNIT.DEN

  • HTML files - HTML_RAMNIT.AJ

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

It infects by appending its code to target host files.

It drops copies of itself in all removable drives. It drops an AUTORUN.INF file to automatically execute the copies it drops when a user accesses the drives of an affected system.

It modifies the Internet Explorer Zone Settings.

  TECHNICAL DETAILS

File Size:

97,102 bytes

File Type:

EXE

Memory Resident:

Yes

Initial Samples Received Date:

27 Jun 2011

Payload:

Modifies the Internet Explorer Zone Settings.

Arrival Details

This file infector 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 file infector then creates the following non-malicious file(s):

  • %User Profile%\{random filename}.log
  • %Program Files%\Internet Explorer\dmlconf.dat

(Note: %User Profile% is the current user's profile folder, which is usually C:\Documents and Settings\{user name} on Windows 2000, XP, and Server 2003, or C:\Users\{user name} on Windows Vista and 7.. %Program Files% is the default Program Files folder, usually C:\Program Files in Windows 2000, Server 2003, and XP (32-bit), Vista (32-bit), and 7 (32-bit), or C:\Program Files (x86) in Windows XP (64-bit), Vista (64-bit), and 7 (64-bit).)

It drops the following copies of itself into the affected system:

  • %User Startup%\{random filename}.exe
  • %Program Files%\{random folder name}\{random filename}.exe

(Note: %User Startup% is the current user's Startup folder, which is usually C:\Windows\Profiles\{user name}\Start Menu\Programs\Startup on Windows 98 and ME, C:\WINNT\Profiles\{user name}\Start Menu\Programs\Startup on Windows NT, and C:\Documents and Settings\{User name}\Start Menu\Programs\Startup.. %Program Files% is the default Program Files folder, usually C:\Program Files in Windows 2000, Server 2003, and XP (32-bit), Vista (32-bit), and 7 (32-bit), or C:\Program Files (x86) in Windows XP (64-bit), Vista (64-bit), and 7 (64-bit).)

It creates the following folders:

  • %Program Files%\{random folder name}

(Note: %Program Files% is the default Program Files folder, usually C:\Program Files in Windows 2000, Server 2003, and XP (32-bit), Vista (32-bit), and 7 (32-bit), or C:\Program Files (x86) in Windows XP (64-bit), Vista (64-bit), and 7 (64-bit).)

Autostart Technique

This file infector modifies the following registry entries to ensure it automatic execution at every system startup:

HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\
Windows NT\CurrentVersion\Winlogon
Userinit = "%System%\userinit.exe,,%Program Files%\{random folder name}\{random file name}.exe"

(Note: The default value data of the said registry entry is %System%\userinit.exe,.)

Other System Modifications

This file infector adds the following registry entries:

HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\
Services\SharedAccess\Parameters\
FirewallPolicy\StandardProfile\AuthorizedApplications\
List
%Program Files%\Internet Explorer\IEXPLORE.EXE = %Program Files%\Internet Explorer\IEXPLORE.EXE:*:Enabled:internet Explorer

File Infection

This file infector infects the following file types:

  • DLL
  • EXE
  • HTML

It infects by appending its code to target host files.

Propagation

This file infector drops copies of itself in all removable drives.

It drops an AUTORUN.INF file to automatically execute the copies it drops when a user accesses the drives of an affected system.

The said .INF file contains the following strings:

[AutoRun]
action=Open
icon=%%WinDir%%\system32\shell32.dll,4
shellexecute=.\RECYCLER\{SID}\{random}.exe
shell\explore\command=.\RECYCLER\{SID}\{random}.exe
USEAUTOPLAY=1
shell\Open\command=.\RECYCLER\{SID}\{random}.exe

Web Browser Home Page and Search Page Modification

This file infector modifies the Internet Explorer Zone Settings.

NOTES:

It opens a hidden instance of IEXPLORE.EXE and connects to remote sites to download and execute possible malicious file(s).

Infected files are detected as follows:

  • DLL and EXE files - PE_RAMNIT.DEN
  • HTML files - HTML_RAMNIT.AJ

  SOLUTION

Minimum Scan Engine:

8.900

FIRST VSAPI PATTERN FILE:

8.252.08

FIRST VSAPI PATTERN DATE:

27 Jun 2011

Step 1

Before doing any scans, Windows XP, Windows Vista, and Windows 7 users must disable System Restore to allow full scanning of their computers.

Step 2

Remove the malware/grayware file dropped/downloaded by PE_RAMNIT.DEN-O

Step 3

Identify and delete files detected as PE_RAMNIT.DEN-O using either the Startup Disk or Recovery Console

[ Learn More ]

Step 4

Restore this modified 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 NT\CurrentVersion\Winlogon
    • From: Userinit = %System%\userinit.exe,,%Program Files%\{random folder name}\{random file name}.exe
      To: %System%\userinit.exe,

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\SYSTEM\CurrentControlSet\Services\SharedAccess\Parameters\FirewallPolicy\StandardProfile\AuthorizedApplications\List
    • %Program Files%\Internet Explorer\IEXPLORE.EXE = %Program Files%\Internet Explorer\IEXPLORE.EXE:*:Enabled:internet Explorer

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.
  • %Program Files%\{random folder name}

Step 7

Search and delete this file

[ Learn More ]
There may be some 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.
  • %Program Files%\Internet Explorer\dmlconf.dat
  • %User Profile%\{random file name}.log

Step 8

Search and delete AUTORUN.INF files created by PE_RAMNIT.DEN-O that contain these strings

[ Learn More ]


[AutoRun]
action=Open
icon=%%WinDir%%\system32\shell32.dll,4
shellexecute=.\RECYCLER\{SID}\{random}.exe
shell\explore\command=.\RECYCLER\{SID}\{random}.exe
USEAUTOPLAY=1
shell\Open\command=.\RECYCLER\{SID}\{random}.exe

Step 9

Scan your computer with your Trend Micro product to delete files detected as PE_RAMNIT.DEN-O. 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 10

Reset Internet security settings

[ Learn More ]


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