RANSOM_ZOLDON.THHAOAH

August 27, 2018
 Analysis by: John Donnie Celestre
 ALIASES:

Trojan-Ransom.Win32.Gen.kgx (KASPERSKY), a variant of Win32/Filecoder.NMJ trojan (NOD32)

 PLATFORM:

Windows

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

  • Threat Type: Ransomware

  • Destructiveness: No

  • Encrypted: No

  • In the wild: Yes

  OVERVIEW

Infection Channel:

Downloaded from the Internet

This Ransomware 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:

1,430,528 bytes

File Type:

EXE

Memory Resident:

Yes

Initial Samples Received Date:

10 Aug 2018

Payload:

Displays message/message boxes, Encrypts files

Arrival Details

This Ransomware arrives on a system as a file dropped by other malware or as a file downloaded unknowingly by users when visiting malicious sites.

Autostart Technique

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

HKEY_CURRENT_USER\Software\Microsoft\
Windows\CurrentVersion\Run
Z0ldon = {malware path}

Other System Modifications

This Ransomware adds the following registry entries as part of its installation routine:

HKEY_CURRENT_USER\Software\Z0ldon
start = {date of malware execution}

Other Details

This Ransomware does the following:

  • Displays the following as part of its ransomware routine:
  • It encrypts files without appending an extension.

Ransomware Routine

This Ransomware leaves text files that serve as ransom notes containing the following text:

  • %User Profile%\DesktopZoldon.txt

  SOLUTION

Minimum Scan Engine:

9.850

FIRST VSAPI PATTERN FILE:

14.434.02

FIRST VSAPI PATTERN DATE:

10 Aug 2018

VSAPI OPR PATTERN File:

14.435.00

VSAPI OPR PATTERN Date:

11 Aug 2018

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

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 3

Restart in Safe Mode

[ Learn More ]

Step 4

Delete this registry key

[ 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
    • Z0ldon

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
    • Z0ldon = {malware path}

Step 6

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.
  • %User Profile%\DesktopZoldon.txt

Step 7

Restart in normal mode and scan your computer with your Trend Micro product for files detected as RANSOM_ZOLDON.THHAOAH. 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 8

Restore encrypted files from backup.


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