Analysis by: Maria Emreen Viray
ALIASES:

Ransom:Win32/Crypmod (MICROSOFT); HEUR:Trojan-Ransom.Win32.Crypmod.gen (KASPERSKY)

 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, Dropped by other malware

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.

It encrypts files found in specific folders.

  TECHNICAL DETAILS

File Size: 16,384 bytes
File Type: EXE
Memory Resident: Yes
Initial Samples Received Date: 30 Jul 2021
Payload: Encrypts files, Modifies system registry

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.

Installation

This Ransomware adds the following processes:

  • to display text in console indicating encryption:
    • %System%\cmd.exe /c echo Ops, seus arquivos foram criptografados
    • %System%\cmd.exe /c pause

(Note: %System% is the Windows system folder, where it usually is C:\Windows\System32 on all Windows operating system versions.)

Other Details

This Ransomware does the following:

  • It displays a simple addition calculator in console while it encrypts files in the background:
    • accepts 2 digits as input
    • outputs sum

Ransomware Routine

This Ransomware encrypts files found in the following folders:

  • C:\Users

It appends the following extension to the file name of the encrypted files:

  • {Original Path\File Name}.{Original Extension}.zip

  SOLUTION

Minimum Scan Engine: 9.800
FIRST VSAPI PATTERN FILE: 16.910.04
FIRST VSAPI PATTERN DATE: 17 Aug 2021
VSAPI OPR PATTERN File: 16.911.00
VSAPI OPR PATTERN Date: 18 Aug 2021

Step 1

Before doing any scans, Windows 7, Windows 8, Windows 8.1, and Windows 10 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

Identify and terminate files detected as Ransom.Win32.CALCRYPT.A

[ 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 4

Scan your computer with your Trend Micro product to delete files detected as Ransom.Win32.CALCRYPT.A. 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 the following Trend Micro Support pages for more information:


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