Modified by: Jeanne Jocson
 PLATFORM:

Windows

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

  • Threat Type: Trojan

  • Destructiveness: No

  • Encrypted:

  • In the wild: Yes

  OVERVIEW

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

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 uses Windows Task Scheduler to create a scheduled task that executes the dropped copy.

It deletes the initially executed copy of itself.

  TECHNICAL DETAILS

File Size: 249,856 bytes
File Type: EXE
Memory Resident: Yes
Initial Samples Received Date: 07 Feb 2016

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 a copy of itself in the following folders using different file names:

  • %Application Data%\Microsoft\Inhovn\inhov.exe

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

It drops the following files:

  • %Application Data%\Microsoft\inhov.wpl
  • %Application Data%\Microsoft\Inhovn\inho.dll

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

It adds the following processes:

  • C:\Windows\explorer.exe

It uses Windows Task Scheduler to create a scheduled task that executes the dropped copy.

Autostart Technique

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

HKEY_CURRENT_USER\Software\Microsoft\
Windows\CurrentVersion\Run
{random characters} = "%Application Data%\Microsoft\Inhovn\inhov.exe"

HKEY_CURRENT_USER\Software\Microsoft\
Windows\CurrentVersion\Run
ctfmon.exe = "%Application Data%\Microsoft\Inhovn\inhov.exe"

The scheduled task executes the malware at the following period:

  • Daily-every 7 hours from the time of creation

Other System Modifications

This Trojan adds the following registry entries:

HKEY_CURRENT_USER\{randomly selected key}\{randomly produced key name}

HKEY_CURRENT_USER\{randomly selected key}\{randomly produced key name}\
Certificates

HKEY_CURRENT_USER\{randomly selected key}\{randomly produced key name}\
CRLs

HKEY_CURRENT_USER\{randomly selected key}\{randomly produced key name}\
CTLs

HKEY_LOCAL_MACHINE\{randomly selected key}\{randomly produced key name}

HKEY_LOCAL_MACHINE\{randomly selected key}\{randomly produced key name}\
Certificates

HKEY_LOCAL_MACHINE\{randomly selected key}\{randomly produced key name}\
CRLs

HKEY_LOCAL_MACHINE\{randomly selected key}\{randomly produced key name}\
CTLs

HKEY_LOCAL_MACHINE\Software\Microsoft\
ESENT\Process\1\
DEBUG
Trace Level = ""

HKEY_LOCAL_MACHINE\Software\Microsoft\
ESENT\Process\inhov\
DEBUG
Trace Level = ""

Other Details

This Trojan deletes the initially executed copy of itself

NOTES:

It enumerates processes and injects its code to explorer.exe and to succeeding processes.

  SOLUTION

Minimum Scan Engine: 9.800
FIRST VSAPI PATTERN FILE: 12.307.50
FIRST VSAPI PATTERN DATE: 31 Jan 2016

Step 1

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 2

Before doing any scans, Windows XP, Windows Vista, and Windows 7 users must disable System Restore to allow full scanning of their computers.

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
    • {random characters} = "%Application Data%\Microsoft\Inhovn\inhov.exe"
  • In HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\Run
    • ctfmon.exe = "%Application Data%\Microsoft\Inhovn\inhov.exe"

Step 4

The following created files/folders/registry keys/registry entries cannot be identified by the user since there are no reference values in the created key. The only way it can be identified is by comparing the present system information with a backup. Note that the said components do not have to be deleted since it won't be harmful to the system.

  • In HKEY_CURRENT_USER\{randomly selected key}\{randomly produced key name}
    • = ""
  • In HKEY_CURRENT_USER\{randomly selected key}\{randomly produced key name}\Certificates
    • = ""
  • In HKEY_CURRENT_USER\{randomly selected key}\{randomly produced key name}\CRLs
    • = ""
  • In HKEY_CURRENT_USER\{randomly selected key}\{randomly produced key name}\CTLs
    • = ""
  • In HKEY_LOCAL_MACHINE\{randomly selected key}\{randomly produced key name}
    • = ""
  • In HKEY_LOCAL_MACHINE\{randomly selected key}\{randomly produced key name}\Certificates
    • = ""
  • In HKEY_LOCAL_MACHINE\{randomly selected key}\{randomly produced key name}\CRLs
    • = ""
  • In HKEY_LOCAL_MACHINE\{randomly selected key}\{randomly produced key name}\CTLs
    • = ""
  • In HKEY_LOCAL_MACHINE\Software\Microsoft\ESENT\Process\1\DEBUG
    • Trace Level = ""
  • In HKEY_LOCAL_MACHINE\Software\Microsoft\ESENT\Process\inhov\DEBUG
    • Trace Level = ""

Step 5

Delete the Scheduled Tasks added by this malware/grayware

[ Learn More ]

To delete the added Scheduled Task file:

For Windows 2000, Windows XP, and Windows Server 2003:

  1. Open the Windows Scheduled Tasks. To do this, click Start>Programs>Accessories>System Tools>Scheduled Tasks.
  2. Double-click on a .JOB file.
  3. Check if the malware path and file name exists in the .JOB file. To do this, check the value in the Run field.
  4. If found, select the .JOB file then press SHIFT+DELETE to permanently delete the file.
  5. Repeat the steps above for the remaining .JOB files.

For Windows Vista, Windows 7, Windows Server 2008, Windows 8, Windows 8.1, and Windows Server 2012:

  1. Open the Windows Task Scheduler. To do this:
    • On Windows Vista, Windows 7, and Windows Server 2008, click Start, type taskschd.msc in the Search input field, then press Enter.
    • On Windows 8, Windows 8.1, and Windows Server 2012, right-click on the lower left corner of the screen, click Run, type taskschd.msc, then press Enter.
  2. In the left panel of the Task Scheduler Window, click Task Scheduler Library.
  3. In the upper-middle panel, click a Task.
  4. In the lower middle panel, click the Actions tab
  5. Check if the malware path and file name exists in the task. To do this, check the value in the Details column under the Actions tab.
  6. If found, select the task and press DELETE and click Yes to delete the task.
  7. Repeat the steps above for the remaining tasks.

Step 6

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