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Ransom.Win32.XCRY.AA

August 15, 2019
 Analysis by: John Anthony Banes
 ALIASES:

RDN/Ransom (McAfee); Trojan-Ransom.Win32.Blocker.lmgo (Kaspersky); Trojan.Win32.Generic!BT (Sunbelt)

 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.

It deletes itself after execution.

It encrypts files with specific file extensions. It drops files as ransom note.

  TECHNICAL DETAILS

File Size:

446,022 bytes

File Type:

EXE

Memory Resident:

No

Initial Samples Received Date:

14 Aug 2019

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.

Installation

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

  • %Application Data%\3b.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(32-bit), XP, and Server 2003(32-bit), or C:\Users\{user name}\AppData\Roaming on Windows Vista, 7, 8, 8.1, 2008(64-bit), 2012(64-bit) and 10(64-bit).)

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
c5d1bf7e77 = "%Application Data%\3b.exe"

Dropping Routine

This Ransomware drops the following files:

  • %Application Data%\lock_file - dropped after encryption, serves as a marker for already-encrypted systems
  • %Application Data%\encryption_key- contains various hashes

(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(32-bit), XP, and Server 2003(32-bit), or C:\Users\{user name}\AppData\Roaming on Windows Vista, 7, 8, 8.1, 2008(64-bit), 2012(64-bit) and 10(64-bit).)

Other Details

This Ransomware deletes itself after execution.

Ransomware Routine

This Ransomware encrypts files with the following extensions:

  • .7z
  • .accdb
  • .arw
  • .bat
  • .bay
  • .c
  • .cdr
  • .cpp
  • .cr2
  • .crw
  • .cs
  • .cs
  • .css
  • .csv
  • .db
  • .dcr
  • .dng
  • .doc
  • .docx
  • .dpr
  • .dpr
  • .dump
  • .dwg
  • .dxf
  • .erf
  • .h
  • .h
  • .hpp
  • .html
  • .j
  • .jav
  • .java
  • .jpeg
  • .jpg
  • .js
  • .json
  • .jsp
  • .kdc
  • .lua
  • .lua
  • .m
  • .M
  • .mef
  • .mm
  • .mrw
  • .nef
  • .nrw
  • .orf
  • .pas
  • .pas
  • .pass
  • .pdf
  • .pef
  • .php
  • .php4
  • .php5
  • .pl
  • .pm
  • .png
  • .pod
  • .ppt
  • .pptx
  • .psd
  • .ptx
  • .py
  • .r3d
  • .raf
  • .rar
  • .raw
  • .rb
  • .rtf
  • .rw2
  • .rwl
  • .sql
  • .sr2
  • .srf
  • .srw
  • .svg
  • .t
  • .tar
  • .tar.gz
  • .tcl
  • .tiff
  • .txt
  • .vb
  • .vhd
  • .vhdx
  • .vmd
  • .vmdk
  • .wallet
  • .xls
  • .xlsx
  • .xml
  • .zip

It avoids encrypting files found in the following folders:

  • C:\Program Files
  • C:\Program Files (x86)
  • C:\Windows

It renames encrypted files using the following names:

  • {encrypted filename}.xcry7684

It drops the following file(s) as ransom note:

  • {folder of encrypted files}\HOW_TO_DECRYPT_FILES.html

  SOLUTION

Minimum Scan Engine:

9.850

FIRST VSAPI PATTERN FILE:

14.878.04

FIRST VSAPI PATTERN DATE:

18 Mar 2019

VSAPI OPR PATTERN File:

14.879.00

VSAPI OPR PATTERN Date:

19 Mar 2019

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.XCRY.AA

[ 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

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
    • c5d1bf7e77 = %Application Data%\3b.exe

Step 5

Search and delete this file

[ 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.
  • %Application Data%\encryption_key
  • {folder of encrypted files}\HOW_TO_DECRYPT_FILES.html

Step 6

Scan your computer with your Trend Micro product to delete files detected as Ransom.Win32.XCRY.AA. 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 7

Restore encrypted files from backup.


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