Analysis by: Francis Xavier Antazo
ALIASES:

a variant of Win32/Kryptik.CZXZ trojan (NOD32)

 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: Downloaded from the Internet, 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 executes then deletes itself afterward.

  TECHNICAL DETAILS

File Size: 410,599 bytes
File Type: EXE
Memory Resident: Yes
Initial Samples Received Date: 06 Mar 2015
Payload: Drops files

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:

  • (Malware Path)\delme.bat
  • %All Users Profile%\Start Menu\Progras\Startup\yiokkbew.exe (detected as TSPY_URSNIF.K)
  • %System Root%\Documents and Settings\Default User\Start Menu\Programs\Startup\yiokkbew.exe (detected as TSPY_URSNIF.K)
  • %User Startup%\yiokkbew.exe (detected as TSPY_URSNIF.K)

(Note: %All Users Profile% is the All Users folder, where it usually is C:\Documents and Settings\All Users on Windows 2000, Windows Server 2003, and Windows XP (32- and 64-bit); C:\ProgramData 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.. %System Root% is the Windows root folder, where it usually is C:\ on all Windows operating system versions.. %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:

  • (Malware Path)\yiokkbew.exe (detected as TSPY_URSNIF.K)

It executes then deletes itself afterward.

Other System Modifications

This Trojan adds the following registry entries:

HKEY_LOCAL_MACHINE\Software\Microsoft\
Windows\CurrentVersion\Run
disable_nasty_checks = "setx SEE_MASK_NOZONECHECKS 1"

  SOLUTION

Minimum Scan Engine: 9.750
FIRST VSAPI PATTERN FILE: 11.536.04
FIRST VSAPI PATTERN DATE: 13 Mar 2015
VSAPI OPR PATTERN File: 11.537.00
VSAPI OPR PATTERN Date: 14 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

Remove the malware/grayware file that dropped/downloaded TROJ_DROPURS.K. (Note: Please skip this step if the threat(s) listed below have already been removed.)

     
    • TSPY_URSNIF.K

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_LOCAL_MACHINE\Software\Microsoft\Windows\CurrentVersion\Run
    • disable_nasty_checks = "setx SEE_MASK_NOZONECHECKS 1"

Step 5

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.
  • (Malware Path)\delme.bat

Step 6

Scan your computer with your Trend Micro product to delete files detected as TROJ_DROPURS.K. 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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