Analysis by: Michael Jay Villanueva

 ALIASES:

RDN/Suspicious.bfr (McAfee); Trojan.Win32.Agent.nevxzp (Kaspersky); W32/Zlader.L!tr (Fortinet)

 PLATFORM:

Windows

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

  • Threat Type: Worm

  • Destructiveness: No

  • Encrypted:

  • In the wild: Yes

  OVERVIEW

Infection Channel: Propagates via flashdrives, Downloaded from the Internet, Dropped by other malware

This worm arrives via removable drives. It 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 the Internet Explorer Zone Settings.

It connects to certain websites to send and receive information. It deletes itself after execution.

  TECHNICAL DETAILS

File Size: 81,920 bytes
File Type: EXE
Memory Resident: No
Initial Samples Received Date: 05 Jul 2016
Payload: Drops files, Connects to URLs/IPs

Arrival Details

This worm arrives via removable drives.

It 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 worm drops the following files:

  • %Application Data%\cabfile.cab
  • {Removable Drive Letter}:\{Shortcut files with the filename of every folder in the removable drive}
    • The malware creates these shortcut files in order to trick the user due to its folder icon and legit filenames.
    • The target path of these shortcuts is set to: %System%\cmd.exe /C ""$RECYCLE.BIN.{GUID}\{GUID}.cmd" && explorer "{GUID folder name - where the original files are stored}""

(Note: %Application Data% is the Application Data folder, where it usually is C:\Documents and Settings\{user name}\Application Data on Windows 2000, Windows Server 2003, and Windows XP (32- and 64-bit); C:\Users\{user name}\AppData\Roaming on Windows Vista (32- and 64-bit), Windows 7 (32- and 64-bit), Windows 8 (32- and 64-bit), Windows 8.1 (32- and 64-bit), Windows Server 2008, and Windows Server 2012.. %System% is the Windows system folder, where it usually is C:\Windows\System32 on all Windows operating system versions.)

It drops the following non-malicious file:

  • %Application Data%\dpx.dll -> serves as a component file used by the malware

(Note: %Application Data% is the Application Data folder, where it usually is C:\Documents and Settings\{user name}\Application Data on Windows 2000, Windows Server 2003, and Windows XP (32- and 64-bit); C:\Users\{user name}\AppData\Roaming on Windows Vista (32- and 64-bit), Windows 7 (32- and 64-bit), Windows 8 (32- and 64-bit), Windows 8.1 (32- and 64-bit), Windows Server 2008, and Windows Server 2012.)

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

  • explorer.exe

Propagation

This worm creates the following folders in all removable drives:

  • {Removable Drive Letter}:\$RECYCLE.BIN.{GUID} -> set attributes to Hidden

It drops copies of itself in the following drives:

  • {Removable Drive Letter}:\$RECYCLE.BIN.{GUID}\{GUID}.{src/pif/cmd} -> Set attribute to Hidden and would look like a shortcut file.

Web Browser Home Page and Search Page Modification

This worm modifies the Internet Explorer Zone Settings.

Other Details

This worm connects to the following website to send and receive information:

  • http://{BLOCKED}ndidnted.com/h/gate.php

It does the following:

  • It renames all the original folders in Removable Drives to: {Removable Drive Letter}:\{random GUIDs}
    • Attributes of these folders are set to Hidden
  • It stops and disables the following windows components by using the following commands:
    • cmd.exe /c net stop SharedAccess
    • cmd.exe /c sc config SharedAccess start=disabled
    • cmd.exe /c net stop wscsvc
    • cmd.exe /c sc config wscsvc start=disabled
    • cmd.exe /c net stop wuauserv
    • cmd.exe /c sc config wuauserv start=disabled
  • It creates .LNK (shortcut) files using folder names found in removable drives. It then hides the original folders tricking users to click .LNK files. This .LNK files point out to a dropped copy of itself in the removable drive.

It deletes itself after execution.

  SOLUTION

Minimum Scan Engine: 9.800
FIRST VSAPI PATTERN FILE: 12.596.02
FIRST VSAPI PATTERN DATE: 17 Jun 2016
VSAPI OPR PATTERN File: 12.597.00
VSAPI OPR PATTERN Date: 18 Jun 2016

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

Note that not all files, folders, and registry keys and entries are installed on your computer during this malware's/spyware's/grayware's execution. This may be due to incomplete installation or other operating system conditions. If you do not find the same files/folders/registry information, please proceed to the next step.

Step 3

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.
  • {Removable Drive Letter}:\$RECYCLE.BIN.{GUID}

Step 4

Search and delete these files

[ 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.
  • %Application Data%\cabfile.cab
  • {Removable Drive Letter}:\{Shortcut files with the filename of every folder in the removable drive}

Step 5

Scan your computer with your Trend Micro product to delete files detected as WORM_ZLADER.B. 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 6

Reset Internet security settings

[ Learn More ]

NOTES:

To retrieve the original files in the removable drive, kindly follow these steps:

  1. In the Start Menu, search for the Folder Options, then in View Tab of the Folder Options window, select Show hidden files, folders, and drives, then uncheck the Hide protected operating system files checkbox. Click OK.
  2. Go to infected Removable Drive Path.
  3. Right-click each HIDDEN folder with a {GUID} filename, then click Properties. Uncheck the Hidden checkbox.
  4. Rename each folder (with a {GUID} folder name) to their appropriate/correct folder name.


Did this description help? Tell us how we did.