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WORM_LETHIC.WSVY

February 02, 2018
 Analysis by: Camille Reyes
 ALIASES:

Trojan:Win32/Dynamer!ac (Microsoft); Gen:Variant.Symmi.38453 (BITDEFENDER)

 PLATFORM:

Windows

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

  • Threat Type: Worm

  • Destructiveness: No

  • Encrypted:

  • 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 terminates itself if it detects it is being run in a virtual environment.

  TECHNICAL DETAILS

File Size:

352,256 bytes

File Type:

EXE

Memory Resident:

Yes

Initial Samples Received Date:

30 Aug 2017

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.

Installation

This Worm drops the following copies of itself into the affected system and executes them:

  • %ProgramData%\{GUID}\{random filename}.exe

(Note: %ProgramData% is the Program Data folder, where it usually is C:\Program Files in Windows 2000, Windows Server 2003, and Windows XP (32- and 64-bit); C:\ProgramData in 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 codes into the following process(es):

  • svchost.exe

Autostart Technique

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

HKEY_CURRENT_USER\Software\Microsoft\
Windows\CurrentVersion\Run
{GUID} = %ProgramData%\{GUID}\{random filename}.exe

Propagation

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

  • {Removable Drive Letter}:\{GUID}\{GUID}.exe

Other Details

This Worm terminates itself if it detects it is being run in a virtual environment.

  SOLUTION

Minimum Scan Engine:

9.850

FIRST VSAPI PATTERN FILE:

13.638.05

FIRST VSAPI PATTERN DATE:

04 Sep 2017

VSAPI OPR PATTERN File:

13.639.00

VSAPI OPR PATTERN Date:

05 Sep 2017

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

Restart in Safe Mode

[ Learn More ]

Step 3

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
    • {GUID} = %ProgramData%\{GUID}\{random filename}.exe

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.
  • %ProgramData%\{GUID}\{random filename}.exe
  • {Removable Drive Letter}:\{GUID}\{GUID}.exe

Step 5

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