RANSOM_CRYPWALL.UAV

 Analysis by: Rhena Inocencio

 PLATFORM:

Windows

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

  • Threat Type: Trojan

  • Destructiveness: No

  • Encrypted:

  • In the wild: Yes

  OVERVIEW

Infection Channel:

Dropped by other malware

This Trojan may be downloaded by other malware/grayware/spyware from remote sites.

It modifies the Internet Explorer Zone Settings.

It deletes the initially executed copy of itself.

  TECHNICAL DETAILS

File Size:

349,696 bytes

File Type:

EXE

Memory Resident:

Yes

Initial Samples Received Date:

21 Jan 2016

Payload:

Connects to URLs/IPs

Arrival Details

This Trojan may be downloaded by other malware/grayware/spyware from remote sites.

Installation

This Trojan drops the following copies of itself into the affected system and executes them:

  • %Application Data%\{random characters}\{random characters}.exe

(Note: %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.)

It drops the following files:

  • %User Startup%\INSTRUCTIONS_{random value}.HTML
  • %User Startup%\INSTRUCTIONS_{random value}.PNG
  • %User Startup%\INSTRUCTIONS_{random value}.TXT
  • %Desktop%\INSTRUCTIONS_{random value}.HTML
  • %Desktop%\INSTRUCTIONS_{random value}.PNG
  • %Desktop%\INSTRUCTIONS_{random value}.TXT
  • {Folder with encrypted files}\INSTRUCTIONS_{random value}.PNG

(Note: %User Startup% is the current user's Startup folder, which is usually C:\Documents and Settings\{user}\Start Menu\Programs\Startup on Windows 2000 and XP, and C:\Documents and Settings\{User name}\Start Menu\Programs\Startup on Windows Vista, 7, and 8.. %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.)

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
{random characters} = "%Application Data%\{random characters}\{random characters}.exe"

Other System Modifications

This Trojan modifies the following file(s):

  • It encrypts files and renames the encrypted files using the following names:
    • {5 to 10 alphanumeric characters}.{2 to 5 alphanumeric characters}

Web Browser Home Page and Search Page Modification

This Trojan modifies the Internet Explorer Zone Settings.

Other Details

This Trojan connects to the following possibly malicious URL:

  • http://{BLOCKED}rts4u.com/dfgOwA.php?{random letter}={random values}
  • http://{BLOCKED}ldirim.net/zn9mur.php?{random letter}={random values}
  • http://{BLOCKED}bear.net/MRGKAC.php?{random letter}={random values}
  • http://{BLOCKED}ouse.nl/iMVfC4.php?{random letter}={random values}
  • http://{BLOCKED}radydrewniane.pl/Fcb7VZ.php?{random letter}={random values}
  • http://{BLOCKED}nat.ro/ZeNpML.php?{random letter}={random values}
  • http://{BLOCKED}fo.kz/LUoMqa.php?{random letter}={random values}
  • http://{BLOCKED}rtners.it/Dd6VPR.php?{random letter}={random values}
  • http://inicc.{BLOCKED}n.gob.mx/UIagAy.php?{random letter}={random values}
  • http://{BLOCKED}p.pl/Si0cCJ.php?{random letter}={random values}
  • http://{BLOCKED}a.com.br/SGJ_Fr.php?{random letter}={random values}
  • http://www.{BLOCKED}nform.netfcb7vz.php/?{random letter}={random values}
  • http://{BLOCKED}n.kz/TSOXQL.php?b={random values}

It deletes the initially executed copy of itself

  SOLUTION

Minimum Scan Engine:

9.800

FIRST VSAPI PATTERN FILE:

12.286.07

FIRST VSAPI PATTERN DATE:

21 Jan 2016

VSAPI OPR PATTERN File:

12.287.00

VSAPI OPR PATTERN Date:

22 Jan 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

Scan your computer with your Trend Micro product and note files detected as RANSOM_CRYPWALL.UAV

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
    • {random characters} = "%Application Data%\{random characters}\{random characters}.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.
  • %User Startup%\INSTRUCTIONS_{random value}.HTML
  • %User Startup%\INSTRUCTIONS_{random value}.PNG
  • %User Startup%\INSTRUCTIONS_{random value}.TXT
  • %Desktop%\INSTRUCTIONS_{random value}.HTML
  • %Desktop%\INSTRUCTIONS_{random value}.PNG
  • %Desktop%\INSTRUCTIONS_{random value}.TXT
  • {Folder with encrypted files}\INSTRUCTIONS_{random value}.PNG

Step 6

Reset Internet security settings

[ Learn More ]

Step 7

Restart in normal mode and scan your computer with your Trend Micro product for files detected as RANSOM_CRYPWALL.UAV. 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 8

Restore this file from backup only Microsoft-related files will be restored. If this malware/grayware also deleted files related to programs that are not from Microsoft, please reinstall those programs on you computer again.

  • Encrypted files with the filename format {5 to 10 alphanumeric characters}.{2 to 5 alphanumeric characters}


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