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Aliases: Trojan:Win32/Tobfy.H (Microsoft), Trojan-Ransom.Win32.Blocker.mnu (Kaspersky), Win32/Injector.ZMK trojan (ESET)
Malware type: Trojan
Destructive: No
Platform: Windows 2000, Windows Server 2003, Windows XP (32-bit, 64-bit), Windows Vista (32-bit, 64-bit), Windows 7 (32-bit, 64-bit)
Encrypted: No
In the wild: Yes


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. It may be downloaded by other malware/grayware from remote sites.

It connects to certain websites to send and receive information.

Technical Details

File size: 45,056 bytes
File type: EXE
Memory resident: Yes
Initial samples received date: 18 Jan 2013
Payload: Collects system information, Connects to URLs/IPs, Blocks user desktop

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.

It may be downloaded by the following malware/grayware from remote sites:


It may be downloaded from the following remote sites:

  • http://{BLOCKED}


This Trojan drops the following copies of itself into the affected system:

  • %Application Data%\{random file name}.exe

(Note: %Application Data% is the current user's Application Data folder, which is usually C:\Documents and Settings\{user name}\Application Data on Windows 2000, XP, and Server 2003, or C:\Users\{user name}\AppData\Roaming on Windows Vista and 7.)

Autostart Technique

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

Microsoft = "%Application Data%\{random file name}.exe"

svñhîst = "{Malware Path and File Name}"

Other System Modifications

This Trojan adds the following registry entries:

SaveZoneInformation = "1"

LowRiskFileTypes = ".exe;"

Other Details

This Trojan connects to the following URL(s) to check for an Internet connection:


It connects to the following website to send and receive information:

  • http://{BLOCKED}
  • http://{BLOCKED}
  • http://{BLOCKED}


It locks the user's screen and displays the aforementioned sites in the screen. However, as of this writing, the said sites are already inaccessible.

It gathers the following information for its ransomware routine:

  • OS version
  • System default language ID
  • System metrics (desktop width and height)


Minimum scan engine: 9.300
First VSAPI Pattern File: 9.662.07
First VSAPI Pattern Release Date: 18 Jan 2013

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

Remove malware/grayware files that dropped/downloaded TROJ_RANSOM.ACV


Step 3

Scan your computer with your Trend Micro product and note files detected as TROJ_RANSOM.ACV

Step 4

Restart in Safe Mode

[ Learn more ]

Step 5

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
    • Microsoft = "%Application Data%\{random file name}.exe"
  • In HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion\Run
    • svñhîst = "{Malware Path and File Name}"
  • In HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\Policies\Attachments
    • SaveZoneInformation = "1"
  • In HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\Policies\Associations
    • LowRiskFileTypes = ".exe;"

Step 6

Restart in normal mode and scan your computer with your Trend Micro product for files detected as TROJ_RANSOM.ACV. 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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Analysis By: Rhena Inocencio

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