TROJ_CRYPWALL.KB

August 03, 2015
 Analysis by: Homer Pacag
 ALIASES:

Trojan:Win32/Skeeyah.A!rfn(Microsoft), Trojan.Cryptodefense(Symantec)

 PLATFORM:

Windows

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

  • Threat Type: Trojan

  • Destructiveness: No

  • Encrypted:

  • In the wild: Yes

  OVERVIEW

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 deletes itself after execution.

  TECHNICAL DETAILS

File Size:

241,664 bytes

File Type:

EXE

Memory Resident:

Yes

Initial Samples Received Date:

03 Aug 2015

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 files:

  • {folders in drives}:\HELP_DECRYPT.HTML
  • {folders in drives}:\HELP_DECRYPT.PNG
  • {folders in drives}:\HELP_DECRYPT.TXT
  • {folders in drives}:\HELP_DECRYPT.URL

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

  • %System Root%\{random}\{random}.exe
  • %Application Data%\{random}.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.)

It creates the following folders:

  • %System Root%\7a2c2a22

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

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} = "%System Root%\{random}\{random}.exe"

HKEY_CURRENT_USER\Software\Microsoft\
Windows\CurrentVersion\Run
{random} = "%Application Data%\{random}.exe"

It drops the following file(s) in the Windows User Startup folder to enable its automatic execution at every system startup:

  • %User Startup%\{random}.exe - copy of itself

(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.)

Other System Modifications

This Trojan modifies the following registry entries:

HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\
Services\wuauserv
Start = "4"

(Note: The default value data of the said registry entry is 2.)

HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\
Services\wscsvc
Start = "4"

(Note: The default value data of the said registry entry is 2.)

HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\
Services\ERSvc
Start = "4"

(Note: The default value data of the said registry entry is 2.)

HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\
Services\BITS
Start = "3"

(Note: The default value data of the said registry entry is 2.)

Other Details

This Trojan connects to the following possibly malicious URL:

  • {BLOCKED}kbox.com.wp-content/themes/ee.php
  • {BLOCKED}icalhealthservices.com.au/wp-content/wp-content/plugins/aa.php
  • {BLOCKED}om.au/wp-content/plugins/bb.php
  • {BLOCKED}m.com/wp-content/themes/cc.php
  • {BLOCKED}ges.com/wp-content/themes/dd.php.
  • {BLOCKED}rabulut.com/wp-content/plugins/aa.php
  • {BLOCKED}sreferralnetwork.com/wp-content/plugins/bb.php
  • {BLOCKED}avelblog.com/wp-content/themes/cc.php
  • {BLOCKED}naboca.com/wp-content/themes/dd.php
  • {BLOCKED}asta.com/wp-content/themes/ee.php
  • {BLOCKED}ledreaming.com/wp-content/themes/aa.php
  • {BLOCKED}rds.com/wp-content/plugins/bb.php.
  • {BLOCKED}ancerswap.com/wp-content/plugins/cc.php
  • {BLOCKED}dadmatters.com/wp-content/themes/dd.php
  • {BLOCKED}kbox.com/wp-content/themes/ee.php.
  • {BLOCKED}ductsinc.com/wp-content/plugins/aa.php
  • {BLOCKED}ex.com/wp-content/plugins/bb.php
  • {BLOCKED}makeupartists.com/wp-content/plugins/bb.php
  • {BLOCKED}lman.com/wp-content/plugins/cc.php
  • {BLOCKED}ctical.com/wp-content/plugins/dd.php
  • {BLOCKED}epromoworks.com/wp-content/plugins/ee.php
  • {BLOCKED}orspeaking.com/wp-content/themes/aa.php
  • {BLOCKED}hirts.com/wp-content/plugins/bb.php
  • {BLOCKED}ts.com/wp-content/themes/cc.php
  • {BLOCKED}e-blah.com/wp-content/plugins/dd.php
  • {BLOCKED}n.com/wp-content/themes/ee.php
  • {BLOCKED}ucklechoppers.com/wp-content/plugins/aa.php
  • {BLOCKED}x.com/wp-content/plugins/bb.php
  • {BLOCKED}sd.com/wp-content/plugins/cc.php
  • {BLOCKED}der.com/wp-content/plugins/dd.php
  • {BLOCKED}larose.com/wp-content/plugins/ee.php
  • {BLOCKED}oersam.com/wp-content/plugins/aa.php
  • {BLOCKED}tapreppersparadise.com/wp-content/plugins/bb.php
  • {BLOCKED}argenutrition.com/wp-content/plugins/cc.php
  • {BLOCKED}abbitartdesign.com/wp-content/plugins/dd.php
  • {BLOCKED}peone.com/wp-content/plugins/ee.php
  • {BLOCKED}nd.com/wp-content/plugins/aa.php
  • {BLOCKED}erynature.com/wp-content/plugins/bb.php.
  • {BLOCKED}x.com/wp-content/plugins/cc.php
  • {BLOCKED}blend.com/wp-content/themes/dd.php
  • {BLOCKED}bontubes.com/wp-content/plugins/ee.php
  • {BLOCKED}qvarnamowers.com/wp-content/themes/aa.php
  • {BLOCKED}nc.com/wp-content/plugins/bb.php

It deletes itself after execution.

NOTES:

This Trojan is capable of encrypting files.