TROJ_CROWTI.ER

 Analysis by: David John Agni

 ALIASES:

Ransom:Win32/Crowti (Microsoft)

 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 the initially executed copy of itself.

  TECHNICAL DETAILS

File Type:

EXE

Memory Resident:

Yes

Initial Samples Received Date:

17 Mar 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 copies of itself into the affected system:

  • %System Root%\{8 Random Value}\{8 Random Value}.exe
  • %Application Data%\{8 Random Value}.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%\{8 Random Value}

(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
{8 Random Value} = "%Application Data%\{8 Random Value}.exe"

HKEY_CURRENT_USER\Software\Microsoft\
Windows\CurrentVersion\Run
{First 7 Characters of {8 Random Value}} = "%System Root%\{8 Random Value}\{8 Random Value}.exe"

HKEY_CURRENT_USER\Software\Microsoft\
Windows\CurrentVersion\RunOnce
*{Second to the Sixth Characters {8 Random Value}} = "%System Root%\{8 Random Value}\{8 Random Value}.exe"

HKEY_CURRENT_USER\Software\Microsoft\
Windows\CurrentVersion\RunOnce
*{Last Seven Characters of {8 Random Value}} = "%Application Data%\{8 Random Value}.exe"

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

  • %User Startup%\{8 Random Value}.exe

(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.)

Other System Modifications

This Trojan adds the following registry keys:

HKEY_CURRENT_USER\Software\{Random Value}

It adds the following registry entries:

HKEY_CURRENT_USER\Software\{Random Value}
0v = "?[DEFAULT] BASEURL....."

HKEY_CURRENT_USER\Software\{Random Value}
1u = "?What happened to your files ?........"

HKEY_CURRENT_USER\Software\{Random Value}\
{Random}
{Value} = "{List of encrypted files}"

Other Details

This Trojan connects to the following possibly malicious URL:

  • {BLOCKED}rfband.info/img1.php?{Random String}
  • {BLOCKED}ian.com/img1.php?{Random String}
  • {BLOCKED}soft.com/img1.php?{Random String}
  • {BLOCKED}eeasset.com/img5.php?{Random String}
  • {BLOCKED}xbjx.com/img2.php?{Random String}
  • {BLOCKED}iet.com/img1.php?{Random String}
  • {BLOCKED}.com/img3.php?{Random String}
  • {BLOCKED}amuslim-online.com/img5.php?{Random String}
  • {BLOCKED}kan-guvenlik.com/img4.php?{Random String}
  • {BLOCKED}italmd.com/img1.php?{Random String}
  • {BLOCKED}us/img4.php?{Random String}
  • {BLOCKED}biaunited.com/img5.php?{Random String}
  • {BLOCKED}nwohnungen-diana.com/img1.php?{Random String}
  • {BLOCKED}ade.com/img2.php?{Random String}
  • {BLOCKED}g8.com/img5.php?{Random String}
  • {BLOCKED}ndtile.net/img3.php?{Random String}
  • {BLOCKED}world.com/img3.php?{Random String}
  • {BLOCKED}salaria.org/img5.php?{Random String}
  • {BLOCKED}a-ng.com/img5.php?{Random String}
  • {BLOCKED}azateonline.com/img3.php?{Random String}
  • {BLOCKED}cyber.com/img2.php?{Random String}
  • {BLOCKED}m.com/img4.php?{Random String}
  • {BLOCKED}09.com/img2.php?{Random String}
  • {BLOCKED}chae.com/img4.php?{Random String}
  • {BLOCKED}loosphoto.com/img4.php?{Random String}
  • {BLOCKED}.com/img3.php?{Random String}
  • {BLOCKED}hurch.com/img2.php?{Random String}
  • {BLOCKED}profreshional.com/img1.php?{Random String}

It deletes the initially executed copy of itself

NOTES:

It encrypts files with certain extensions in the affected system hard drive.

It drops the following files to all folders where files are encrypted:

  • HELP_DECRYPT.HTML
  • HELP_DECRYPT.TXT
  • HELP_DECRYPT.PNG
  • HELP_DECRYPT

  SOLUTION

Minimum Scan Engine:

9.750

FIRST VSAPI PATTERN FILE:

11.556.03

FIRST VSAPI PATTERN DATE:

17 Mar 2015

VSAPI OPR PATTERN File:

11.557.00

VSAPI OPR PATTERN Date:

18 Mar 2015

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

Restart in Safe Mode

[ Learn More ]

Step 4

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.  
  • %Application Data%\{8 Random Value}.exe
  • %User Startup%\{8 Random Value}.exe

Step 5

Search and delete these folders

[ Learn More ]
Please make sure you check the Search Hidden Files and Folders checkbox in the More advanced options option to include all hidden folders in the search result.
  • %System Root%\{8 Random Value}

Step 6

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
    • {8 Random Value} = "%Application Data%\{8 Random Value}.exe"
  • In HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\Run
    • {First 7 Characters of {8 Random Value}} = "%System Root%\{8 Random Value}\{8 Random Value}.exe"
  • In HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\RunOnce
    • *{Second to the Sixth Characters {8 Random Value}} = "%System Root%\{8 Random Value}\{8 Random Value}.exe"
  • In HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\RunOnce
    • *{Last Seven Characters of {8 Random Value}} = "%Application Data%\{8 Random Value}.exe"

Step 7

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
    • {Random Value}

Step 8

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


Did this description help? Tell us how we did.