Analysis by: Warren Adam Sto. Tomas
ALIASES:

MSIL/Agent.SW!worm (Fortinet)

 PLATFORM:

Windows

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

  • Threat Type: Worm

  • Destructiveness: No

  • Encrypted: No

  • In the wild: Yes

  OVERVIEW

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

  TECHNICAL DETAILS

File Size: 11,259,904 bytes
File Type: EXE
Memory Resident: No
Initial Samples Received Date: 31 Jul 2019

Arrival Details

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

It may be dropped by the following malware:

Installation

This Worm drops the following files:

Other System Modifications

This Worm modifies the following registry entries:

HKEY_CURRENT_USER\Software\Microsoft\
Windows\CurrentVersion\Explorer\
Advanced
HideFileExt = 1

(Note: The default value data of the said registry entry is {User Preference}.)

It modifies the following registry entries to hide files with Hidden attributes:

HKEY_CURRENT_USER\Software\Microsoft\
Windows\CurrentVersion\Explorer\
Advanced
Hidden = 2

(Note: The default value data of the said registry entry is {User Preference}.)

Propagation

This Worm creates the following folders in all removable drives:

  • {removable drive}:\$LimeUSB -> contains original files and folders which were replaced with infected files
  • {removable drive}:\$LimeUSB\LimeIcons -> contains original files' icons

It drops the following copy(ies) of itself in all removable drives:

  • {removable drives}:\$LimeUSB\LimeUSB.exe

Other Details

This Worm does the following:

  • It searches recursively for files in removable drives. For any files or folder it finds, it will move the file/folder in {removable drives}:\$LimeUSB folder
  • It compiles files it found in C# .NET executable and renames it to {original file path}\{original file name and extension}.scr
  • The compiled file will execute the following files:
    • {removable drives}:\$LimeUSB\{original file}
    • {removable drives}:\$LimeUSB\LimeUSB.exe
    • {removable drives}:\$LimeUSB\SydneyFortniteHacks.exe

  SOLUTION

Minimum Scan Engine: 9.850
FIRST VSAPI PATTERN FILE: 15.280.01
FIRST VSAPI PATTERN DATE: 05 Aug 2019
VSAPI OPR PATTERN File: 15.281.00
VSAPI OPR PATTERN Date: 06 Aug 2019

Step 1

Before doing any scans, Windows 7, Windows 8, Windows 8.1, and Windows 10 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

Identify and terminate files detected as Worm.MSIL.LIME.AA

[ Learn More ]
  1. Windows Task Manager may not display all running processes. In this case, please use a third-party process viewer, preferably Process Explorer, to terminate the malware/grayware/spyware file. You may download the said tool here.
  2. If the detected file is displayed in either Windows Task Manager or Process Explorer but you cannot delete it, restart your computer in safe mode. To do this, refer to this link for the complete steps.
  3. If the detected file is not displayed in either Windows Task Manager or Process Explorer, continue doing the next steps.

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_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\Explorer\Advanced
    • Hidden = 2
  • In HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\Explorer\Advanced
    • HideFileExt = 1

Step 5

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.
  • {removable drives}:\$LimeUSB\SydneyFortniteHacks.exe
  • {removable drives}:\$LimeUSB\LimeUSB.exe

Step 6

Scan your computer with your Trend Micro product to delete files detected as Worm.MSIL.LIME.AA. 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 the following Trend Micro Support pages for more information:


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