Analysis by: RonJay Kristoffer Caragay
ALIASES:

Ransom:MSIL/Samas.A (Microsoft); Trojan-Ransom.MSIL.Samas.as (Kaspersky); Ransom.FileCryptor (Malwarebytes); a variant of MSIL/Filecoder.Samas.B (ESET-NOD32); Win32:Ransom-AYO [Trj] (Avast)

 PLATFORM:

Windows

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

  • 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.

  TECHNICAL DETAILS

File Size: 53,248 bytes
File Type: EXE
Initial Samples Received Date: 10 Jan 2017

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 and executes the following files:

  • %All Users Profile%\Application Data\Msdtc\mustupdate.bat

(Note: %All Users Profile% is the All Users folder, where it usually is C:\Documents and Settings\All Users on Windows 2000, Windows Server 2003, and Windows XP (32- and 64-bit); C:\ProgramData 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.)

Other Details

This Trojan renames encrypted files using the following names:

  • {Original Filename and Extension}.deria.wowreadfordecryp

It drops the following file(s)/component(s):

  • %Desktop%\{numbers}-WOW-READ-FOR-DECRYP.html

(Note: %Desktop% is the desktop folder, where it usually is C:\Documents and Settings\{user name}\Desktop in Windows 2000, Windows Server 2003, and Windows XP (32- and 64-bit); C:\Users\{user name}\Desktop 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.)