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RANSOM_CRYPZXAS.B

August 29, 2016
 Analysis by: Francis Xavier Antazo
 ALIASES:

a variant of MSIL/Filecoder.CA (ESET);

 PLATFORM:

Windows

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

  • Threat Type: Trojan

  • Destructiveness: No

  • Encrypted: Yes

  • In the wild: Yes

  OVERVIEW

Infection Channel:

Downloaded from the Internet


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.

  TECHNICAL DETAILS

File Size:

67584 bytes

File Type:

EXE

Memory Resident:

Yes

Initial Samples Received Date:

11 Aug 2016

Payload:

Connects to URLs/IPs, Encrypts files

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 adds the following processes:

  • excel.exe

Other Details

This Trojan encrypts files with the following extensions:

  • .1cd
  • .7z
  • .accdb
  • .ai
  • .arj
  • .arw
  • .bmp
  • .cd
  • .cdr
  • .cr2
  • .db
  • .dbf
  • .doc
  • .docx
  • .epf
  • .jpeg
  • .jpg
  • .ldf
  • .max
  • .md
  • .mdb
  • .mdf
  • .nef
  • .nrf
  • .odb
  • .odg
  • .ods
  • .odt
  • .orf
  • .pdf
  • .png
  • .ppt
  • .pptx
  • .psd
  • .rar
  • .rtf
  • .sr2
  • .srf
  • .tar
  • .tif
  • .xls
  • .xlsx
  • .zip

It renames encrypted files using the following names:

  • {original filename and file extension}.blocked

NOTES:

This ransomware drops the following files whenever it is able to successfully encrypt files:

  • keyvalue.bin
  • !!!!!!!! c3 8a c3 a0 c3 aa c3 a2 c3 ae c3 b1 c3 b1 c3 b2 c3 a0 c3 ad c3 ae c3 a2 c3 a8 c3 b2 c3 bc c3 b4 c3 a0 c3 a9 c3 ab c3 bb!!!!!!!.txt

It avoids encrypting files in the following folders:

  • %System%
  • %Program Files%
  • System Volume Information
  • $RECYCLE.BIN
  • RECYCLER

It executes the following to delete shadow copies:

vssadmin.exe Delete Shadows /All /Quiet

It encrypts files in fixed and network drives. It performs net view and finds диск which is Russian for Disk. It then tries to encrypt on the shared network disk resources it finds.

  SOLUTION

Minimum Scan Engine:

9.800

FIRST VSAPI PATTERN FILE:

12.710.05

FIRST VSAPI PATTERN DATE:

12 Aug 2016

VSAPI OPR PATTERN File:

12.711.00

VSAPI OPR PATTERN Date:

13 Aug 2016

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

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.  
  • keyvalue.bin
  • !!!!!!!!Êàê âîññòàíîâèòü ôàéëû!!!!!!!.txt

Step 4

Scan your computer with your Trend Micro product to delete files detected as RANSOM_CRYPZXAS.B. 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 5

Restore encrypted files from backup.


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