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Ransom_CRYPTESLA.YUYAHL

February 23, 2016
 PLATFORM:

Windows

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

  • 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:

269,312 bytes

File Type:

EXE

Memory Resident:

Yes

Initial Samples Received Date:

23 Feb 2016

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:

  • %User Profile%\Application Data\qqxakbm.exe

(Note: %User Profile% is the current user's profile folder, which is usually C:\Documents and Settings\{user name} on Windows 2000, XP, and Server 2003, or C:\Users\{user name} on Windows Vista and 7.)

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
werity-32452345 = "%User Profile%\Application Data\qqxakbm.exe"

HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\
Windows\CurrentVersion\Run
werity-32452345 = "%User Profile%\Application Data\qqxakbm.exe"

Other System Modifications

This Trojan deletes the following files:

  • {malware path and file name}:zone.identifier
  • %User Profile%\Application Data\qqxakbm.exe:Zone.Identifier
  • %User Profile%\APPLIC~1\qqxakbm.exe

(Note: %User Profile% is the current user's profile folder, which is usually C:\Documents and Settings\{user name} on Windows 2000, XP, and Server 2003, or C:\Users\{user name} on Windows Vista and 7.)

It adds the following registry keys:

HKEY_CURRENT_USER\Software\xxxsys

HKEY_CURRENT_USER\Software\337EA6FF33DC515C

It adds the following registry entries:

HKEY_CURRENT_USER\Software\xxxsys
ID = "{random values}"

HKEY_CURRENT_USER\Software\337EA6FF33DC515C
data = "{random values}"

HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\
Windows\CurrentVersion\policies\
system
EnableLinkedConnections = "1"

Dropping Routine

This Trojan drops the following files:

  • %User Profile%\My Documents\recover_file_mxjpkxlfm.txt
  • %Desktop%\help_recover_instructions.TXT
  • %Desktop%\help_recover_instructions.HTM

(Note: %User Profile% is the current user's profile folder, which is usually C:\Documents and Settings\{user name} on Windows 2000, XP, and Server 2003, or C:\Users\{user name} on Windows Vista and 7.. %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.)

Other Details

This Trojan connects to the following possibly malicious URL:

  • http://bddadmin.{BLOCKED}dins.fr
  • {BLOCKED}.179.58

It deletes itself after execution.

This report is generated via an automated analysis system.

  SOLUTION

Minimum Scan Engine:

9.8

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

Restart in Safe Mode

[ Learn More ]

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.

  • In HKEY_CURRENT_USER\Software
    • xxxsys
  • In HKEY_CURRENT_USER\Software
    • 337EA6FF33DC515C

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
    • werity-32452345 = "%User Profile%\Application Data\qqxakbm.exe"
  • In HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion\Run
    • werity-32452345 = "%User Profile%\Application Data\qqxakbm.exe"
  • In HKEY_CURRENT_USER\Software\xxxsys
    • ID = "{random values}"
  • In HKEY_CURRENT_USER\Software\337EA6FF33DC515C
    • data = "{random values}"
  • In HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion\policies\system
    • EnableLinkedConnections = "1"

Step 5

Search and delete these components

[ Learn More ]
There may be some components 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 Profile%\My Documents\recover_file_mxjpkxlfm.txt
  • %Desktop%\help_recover_instructions.TXT
  • %Desktop%\help_recover_instructions.HTM

Step 6

Restart in normal mode and scan your computer with your Trend Micro product for files detected as Ransom_CRYPTESLA.YUYAHL. 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 7

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.

  • {malware path and file name}:zone.identifier
  • %User Profile%\Application Data\qqxakbm.exe:Zone.Identifier
  • %User Profile%\APPLIC~1\qqxakbm.exe


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