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Ransom.Win64.NEFILIM.AC

January 16, 2021
 Analysis by: Mohammed Malubay
 ALIASES:

Trojan-Ransom.Nemty(IKARUS);

 PLATFORM:

Windows

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

  • Threat Type: Ransomware

  • Destructiveness: No

  • Encrypted: Yes

  • 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.

It avoids encrypting files with the following file extensions.

  TECHNICAL DETAILS

File Size:

3,175,984 bytes

File Type:

EXE

Memory Resident:

No

Initial Samples Received Date:

16 Jan 2021

Payload:

Encrypts files, Displays message/message boxes

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.

Other Details

This Ransomware does the following:

  • It encrypts all local drives.
  • The strings and extensions being avoided are case sensitive.
  • It displays the following error logs of files and folders that it attempted but failed to encrypt.

Ransomware Routine

This Ransomware avoids encrypting files with the following strings in their file path:

  • Windows
  • AppData
  • Program Files

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

  • .DERZKO

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

  • {Encrypted Directory}\DERZKO-HELP.txt

It avoids encrypting files with the following file extensions:

  • .sys
  • .dll
  • .exe
  • .url
  • .lnk
  • DERZKO

  SOLUTION

Minimum Scan Engine:

9.800

FIRST VSAPI PATTERN FILE:

16.480.05

FIRST VSAPI PATTERN DATE:

16 Jan 2021

VSAPI OPR PATTERN File:

16.481.00

VSAPI OPR PATTERN Date:

17 Jan 2021

Step 1

Trend Micro Predictive Machine Learning detects and blocks malware at the first sign of its existence, before it executes on your system. When enabled, your Trend Micro product detects this malware under the following machine learning name:

  • Ransom.Win32.TRX.XXPE50FFF039E0002

Step 2

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 3

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 4

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.
  • {Encrypted Directory}\DERZKO-HELP.txt

Step 5

Scan your computer with your Trend Micro product to delete files detected as Ransom.Win64.NEFILIM.AC. 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:

Step 6

Restore encrypted files from backup.


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