ALIASES:

Ransom:Win32/Crowti.A (Microsoft)

 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: 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. However, as of this writing, the said sites are inaccessible.

  TECHNICAL DETAILS

File Size: 266,306 bytes
File Type: EXE
Memory Resident: Yes
Initial Samples Received Date: 16 Oct 2014
Payload: Encrypts files, Connects to URLs/IPs

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 folders:

  • %System Root%\{7 characters from UID}

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

It drops the following files:

  • %User Startup%\DECRYPT_INSTRUCTION.TXT
  • %User Startup%\DECRYPT_INSTRUCTION.HTML
  • %User Startup%\INSTALL_TOR.URL

(Note: %User Startup% is the current user's Startup folder, which is usually C:\Windows\Profiles\{user name}\Start Menu\Programs\Startup on Windows 98 and ME, C:\WINNT\Profiles\{user name}\Start Menu\Programs\Startup on Windows NT, and C:\Documents and Settings\{User name}\Start Menu\Programs\Startup.)

It drops and executes the following files:

  • %Desktop%\DECRYPT_INSTRUCTION.TXT
  • %Desktop%\DECRYPT_INSTRUCTION.HTML
  • %Desktop%\INSTALL_TOR.URL

(Note: %Desktop% is the desktop folder, where it usually is C:\Documents and Settings\{user name}\Desktop in Windows 2000, Windows Server 2003, and Windows XP (32- and 64-bit); C:\Users\{user name}\Desktop in 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.)

It drops the following copies of itself into the affected system:

  • %System Root%\{7 characters from UID}\{7 characters from UID}.exe
  • %Application Data%\{7 characters from UID}.exe
  • %User Startup%\{7 characters from UID}.exe

(Note: %System Root% is the Windows root folder, where it usually is C:\ on all Windows operating system versions.. %Application Data% is the Application Data folder, where it usually is C:\Documents and Settings\{user name}\Application Data on Windows 2000, Windows Server 2003, and Windows XP (32- and 64-bit); C:\Users\{user name}\AppData\Roaming 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.. %User Startup% is the current user's Startup folder, which is usually C:\Windows\Profiles\{user name}\Start Menu\Programs\Startup on Windows 98 and ME, C:\WINNT\Profiles\{user name}\Start Menu\Programs\Startup on Windows NT, and C:\Documents and Settings\{User name}\Start Menu\Programs\Startup.)

Autostart Technique

This Trojan adds the following registry entries to enable its automatic execution at every system startup:

HKEY_CURRENT_USER\Software\Microsoft\
Windows\CurrentVersion\Run
{7characters from UID} = "%Application Data%\{7 characters from UID}.exe"

HKEY_CURRENT_USER\Software\Microsoft\
Windows\CurrentVersion\Run
{6 characters from UID} = "%System Root%\{7 characters from UID}\{7 characters from UID}.exe"

Other System Modifications

This Trojan adds the following registry keys:

HKEY_CURRENT_USER\Software\Vocal AppWizard-Generated Applications

HKEY_CURRENT_USER\Software\Vocal AppWizard-Generated Applications\
{random}

HKEY_CURRENT_USER\Software\Vocal AppWizard-Generated Applications\
{random}\Recent File List

HKEY_CURRENT_USER\Software\Vocal AppWizard-Generated Applications\
{random}\Settings

Other Details

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

  • http://www.{BLOCKED}times.com/{random value}
  • http://www.{BLOCKED}yapmak.com/{random value}
  • http://{BLOCKED}rtner.cz/{random value}
  • http://{BLOCKED}tfolio.ccpullman.ca/blog/{random value}
  • http://www.{BLOCKED}umann.de/{random value}
  • http://{BLOCKED}phsphotography.co.uk/blog/{random value}
  • http://www.{BLOCKED}elifesupport.com/{random value}
  • http://www.{BLOCKED}cole.be/{random value}
  • http://www.{BLOCKED}ownguild.com//{random value}

It encrypts files with the following extensions:

  • .aif
  • .aifc
  • .aiff
  • .asf
  • .asx
  • .au
  • .bmp
  • .dib
  • .doc
  • .dot
  • .dvr-ms
  • .emf
  • .gif
  • .hta
  • .htm
  • .html
  • .ico
  • .jfif
  • .jpe
  • .jpeg
  • .jpg
  • .m1v
  • .m3u
  • .mid
  • .midi
  • .mp2
  • .mp2v
  • .mp3
  • .mpa
  • .mpe
  • .mpeg
  • .mpg
  • .pdf
  • .png
  • .pot
  • .pps
  • .ppt
  • .rle
  • .rmi
  • .rtf
  • .snd
  • .tif
  • .tiff
  • .wav
  • .wax
  • .wm.mpv2
  • .wma
  • .wmf
  • .wmv
  • .wmx
  • .wvx
  • .xls
  • .xlt
  • .xlw
  • .xml
  • .zip

However, as of this writing, the said sites are inaccessible.

NOTES:

It drops DECRYPT_INSTRUCTION.TXT, DECRYPT_INSTRUCTION.HTML, and INSTALL_TOR.URL to all folders where files are encrypted.

  SOLUTION

Minimum Scan Engine: 9.700
FIRST VSAPI PATTERN FILE: 11.214.06
FIRST VSAPI PATTERN DATE: 15 Oct 2014
VSAPI OPR PATTERN File: 11.215.00
VSAPI OPR PATTERN Date: 15 Oct 2014

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

Scan your computer with your Trend Micro product and note files detected as TROJ_CROWTI.UHU

Step 3

Restart in Safe Mode

[ Learn More ]

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
    • {7characters from UID} = "%Application Data%\{7 characters from UID}.exe"
  • In HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\Run
    • {6 characters from UID} = "%System Root%\{7 characters from UID}\{7 characters from UID}.exe"

Step 5

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.

  • In HKEY_CURRENT_USER\Software
    • Vocal AppWizard-Generated Applications

Step 6

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.  
  • DECRYPT_INSTRUCTION.TXT
  • DECRYPT_INSTRUCTION.HTML
  • INSTALL_TOR.URL

Step 7

Restart in normal mode and scan your computer with your Trend Micro product for files detected as TROJ_CROWTI.UHU. 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.


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