Analysis by: Cris Nowell Pantanilla

ALIASES:

Ransom:Win32/DMALocker (Microsoft), HEUR:Trojan-Ransom.Win32.Agent.ilw (Kaspersky),

 PLATFORM:

Windows

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

  • Threat Type: Trojan

  • Destructiveness: No

  • Encrypted: Yes

  • In the wild: Yes

  OVERVIEW

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

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 Type: EXE
Memory Resident: Yes
Initial Samples Received Date: 15 Feb 2017
Payload: Displays message/message boxes, Encrypts files

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

  • C:\ProgramData\svchosd.exe
  • C:\Documents and Settings\All Users\svchosd.exe

It drops the following files:

  • C:\Documents and Settings\All Users\cryptinfo.txt ← ransom note
  • C:\Documents and Settings\All Users\decrypting.txt ← encryption done marker
  • C:\Documents and Settings\All Users\start.txt ← encryption start marker
  • C:\ProgramData\cryptinfo.txt ← ransom note
  • C:\ProgramData\decrypting.txt ← encryption done marker
  • C:\ProgramData\start.txt ← encryption start marker

Autostart Technique

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

HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\
Windows\CurrentVersion\Run
Windows Firewall = "C:\Documents and Settings\All Users\svchosd.exe"

HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\
Windows\CurrentVersion\Run
Windows Update = "notepad C:\Documents and Settings\All Users\cryptinfo.txt"

File Infection

This Trojan avoids infecting the following file types:

  • .exe
  • .msi
  • .dll
  • .pif
  • .scr
  • .sys
  • .msp
  • .com
  • .lnk
  • .hta
  • .cpl
  • .cmd

It avoids infecting folders containing the following strings:

  • \Windows\
  • \WINDOWS\
  • Games
  • \Temp
  • \Sample Pictures
  • \Sample Music
  • \cache
  • \Cache

Other Details

This Trojan does the following:

  • It avoids encrypting Floppy and CDRom Drives.

NOTES:

The ransomware displays the following ransom note window:

  SOLUTION

Minimum Scan Engine: 9.850
FIRST VSAPI PATTERN FILE: 12.940.03
FIRST VSAPI PATTERN DATE: 15 Feb 2017
VSAPI OPR PATTERN File: 12.941.00
VSAPI OPR PATTERN Date: 16 Feb 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

Identify and terminate files detected as RANSOM_DMALOCKER.AUSX

[ 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 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_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion\Run
    • Windows Firewall = "C:\Documents and Settings\All Users\svchosd.exe"
  • In HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion\Run
    • Windows Update = "notepad C:\Documents and Settings\All Users\cryptinfo.txt"

Step 4

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.
C:\Documents and Settings\All Users\cryptinfo.txt
C:\Documents and Settings\All Users\decrypting.txt
C:\Documents and Settings\All Users\start.txt
C:\ProgramData\cryptinfo.txt
C:\ProgramData\decrypting.txt
C:\ProgramData\start.txt

Step 5

Scan your computer with your Trend Micro product to delete files detected as RANSOM_DMALOCKER.AUSX. 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

Restore encrypted files from backup.


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