RANSOM_CRYPAPP.A

 Analysis by: Anthony Joe Melgarejo

 ALIASES:

Ransom:Win32/KeepLock.A (Microsoft)

 PLATFORM:

Windows

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

  • Threat Type: Trojan

  • Destructiveness: No

  • Encrypted: No

  • In the wild: Yes

  OVERVIEW

Infection Channel:

Downloaded from the Internet, Dropped by other malware

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.

It connects to certain websites to send and receive information.

  TECHNICAL DETAILS

File Size:

4,176,384 bytes

File Type:

EXE

Memory Resident:

No

Initial Samples Received Date:

20 Aug 2015

Payload:

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 drops the following component file(s):

  • %User Temp%\keepalive.exe - also detected as RANSOM_CRYPAPP.A

(Note: %User Temp% is the user's temporary folder, where it usually is C:\Documents and Settings\{user name}\Local Settings\Temp on Windows 2000, Windows Server 2003, and Windows XP (32- and 64-bit); C:\Users\{user name}\AppData\Local\Temp on Windows Vista (32- and 64-bit), Windows 7 (32- and 64-bit), Windows 8 (32- and 64-bit), Windows 8.1 (32- and 64-bit), Windows Server 2008, and Windows Server 2012.)

Other System Modifications

This Trojan adds the following registry entries:

HKEY_CURRENT_USER\Software\Microsoft\
Windows\CurrentVersion\Run
CryptoAppDelay = {multiple entries}

HKEY_CURRENT_USER\Software\Microsoft\
Windows\CurrentVersion\Run
CryptoAppAppForcedEnded = "1"

HKEY_CURRENT_USER\Software\CryptoApp\
scrsss\progress
files = {number of files encrypted}

HKEY_CURRENT_USER\Software\CryptoApp\
scrsss\progress
done = {infection status}

HKEY_CURRENT_USER\Software\CryptoApp\
scrsss\progress
mode = 2

It adds the following registry keys as part of its installation routine:

HKEY_CURRENT_USER\Software\CryptoApp\
scrsss\progress

Download Routine

This Trojan connects to the following website(s) to download and execute a malicious file:

  • http://www.{BLOCKED}av.sk/media/csrsss.exe
  • http://{BLOCKED}.{BLOCKED}.82.98/tmp/csrsss.exe
  • http://{BLOCKED}gclip.ru/media/csrsss.exe
  • http://{BLOCKED}allphoenix.com/media/csrsss.exe
  • http://{BLOCKED}auto.pl/media/csrsss.exe

It saves the files it downloads using the following names:

  • %System%\scsrss.exe - also detected as RANSOM_CRYPAPP.A

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

Other Details

This Trojan connects to the following website to send and receive information:

  • http://{BLOCKED}repairsystems.com/ksubmit.php/bitcoin_address={bitcoin payment address}&empid={victim ID}&comp={computer name}&ipv4={ victim IP address}&blkk={value}&publ={encryption public key}&priv={encryption private key}
  • http://{BLOCKED}repairsystems.com/kretrieve.php/empid={victim ID}&comp={computer name}&ipv4={victim IP address}

It encrypts files with the following extensions:

  • .iff
  • .3fr
  • .3gp
  • .7z
  • .accdb
  • .ai
  • .arc
  • .arw
  • .avi
  • .bad
  • .bay
  • .bmp
  • .cam
  • .cdr
  • .cer
  • .cineon
  • .cr2
  • .crt
  • .crw
  • .csv
  • .ctl
  • .dat
  • .dbf
  • .dcr
  • .der
  • .des
  • .dicom
  • .dng
  • .doc
  • .docm
  • .docx
  • .dsc
  • .dwg
  • .dxf
  • .dxg
  • .eps
  • .erf
  • .fla
  • .flv
  • .fmb
  • .fmt
  • .fmx
  • .gif
  • .hdr
  • .html
  • .iif
  • .img
  • .indd
  • .jpe
  • .jpeg
  • .jpg
  • .kdc
  • .log
  • .lst
  • .m4v
  • .mdb
  • .mdf
  • .mef
  • .mov
  • .mpeg
  • .mrw
  • .nd
  • .nef
  • .nrw
  • .odb
  • .odm
  • .odp
  • .ods
  • .odt
  • .openexr
  • .ora
  • .orf
  • .p12
  • .p7b
  • .p7c
  • .pbm
  • .pck
  • .pdd
  • .pdf
  • .pef
  • .pem
  • .pfx
  • .pgm
  • .pic
  • .pkb
  • .pks
  • .plb
  • .pls
  • .png
  • .pot
  • .ppm
  • .pps
  • .ppt
  • .pptm
  • .pptx
  • .prn
  • .psb
  • .psd
  • .pst
  • .ptx
  • .qba
  • .tlg
  • .qbm
  • .qbr
  • .qbw
  • .qbw
  • .tlg
  • .qbx
  • .qby
  • .qfx
  • .r3d
  • .raf
  • .rar
  • .raw
  • .rdf
  • .rdo
  • .rep
  • .rex
  • .rtf
  • .rw2
  • .rwl
  • .sql
  • .srf
  • .srw
  • .sti
  • .sxi
  • .tiff
  • .txt
  • .vdi
  • .wb2
  • .wpd
  • .wps
  • .xbm
  • .xlk
  • .xls
  • .xlsb
  • .xlsm
  • .xlsx
  • .xml
  • .yaml
  • .zip
  • .php
  • .css
  • .asp
  • .cpp
  • .c
  • .js
  • .pl
  • .perl
  • .swf
  • .aspx
  • .potx
  • .potm
  • .ppam
  • .ppsx
  • .ppsm
  • .sldx
  • .sldm
  • .thmx
  • .xlam
  • .xltm
  • .dotm
  • .dotx

It renames encrypted files using the following names:

  • {orginal filename and extension}.encrypted

NOTES:
It displays a ransom note:

  SOLUTION

Minimum Scan Engine:

9.750

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

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. Before you could do this, you must restart in Safe Mode. For instructions on how to do this, you may refer to this page If the preceding step requires you to restart in safe mode, you may proceed to edit the system registry.

  • In HKEY_CURRENT_USER\Software\CryptoApp\scrsss
    • progress

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
    • CryptoAppDelay = {multiple entries}
  • In HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\Run
    • CryptoAppAppForcedEnded = "1"

Step 5

Scan your computer with your Trend Micro product to delete files detected as RANSOM_CRYPAPP.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 this Knowledge Base page for more information.

NOTES:

Perform this step as the last step of the Solution:

Restore encrypted files from backup.


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