Analysis by: Patrick Angelo Roderno
ALIASES:

Gen:Variant.Razy.178861 (BITDEFENDER); Trojan.Gen.2 (NORTON); HEUR:Trojan-Ransom.Win32.Generic (KASPERSKY)

 PLATFORM:

Windows

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

  • Threat Type: Ransomware

  • Destructiveness: No

  • Encrypted: Yes

  • In the wild: Yes

  OVERVIEW

Infection Channel: Dropped by other malware, Downloaded from the Internet

This Ransomware arrives on a system as a file dropped by other malware or as a file downloaded unknowingly by users when visiting malicious sites.

It drops files as ransom note.

  TECHNICAL DETAILS

File Size: 113,152 bytes
File Type: EXE
Memory Resident: No
Initial Samples Received Date: 29 May 2017
Payload: Displays message/message boxes, Encrypts files

Arrival Details

This Ransomware arrives on a system as a file dropped by other malware or as a file downloaded unknowingly by users when visiting malicious sites.

Dropping Routine

This Ransomware drops the following files:

  • %Start Menu%\Programs\Startup\HOW DECRIPT FILES.hta
  • %Desktop%\{generated random 40-letter string}.txt

(Note: %Start Menu% is the Start Menu folder, where it usually is C:\Documents and Settings\{user name}\Start Menu on Windows 2000, Windows Server 2003, and Windows XP (32- and 64-bit); C:\Users\{user name}\AppData\Roaming\Microsoft\Windows\Start Menu 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.. %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 Ransomware displays the following message boxes:


Ransomware Routine

This Ransomware avoids encrypting files with the following strings in their file name:

  • HOW DECRIPT FILES.hta
  • {generated random 40-letter string}.txt
  • bootmgr
  • BOOTNXT
  • pagefile.sys
  • swapfile.sys
  • hiberfil.sys
  • loadmgr

It avoids encrypting files with the following strings in their file path:

  • System32

It renames encrypted files using the following names:

  • trulolo@{BLOCKED}a.com_{random characters}

It drops the following file(s) as ransom note:

  • {Folders with affected files}\HOW DECRIPT FILES.hta

  SOLUTION

Minimum Scan Engine: 9.850
FIRST VSAPI PATTERN FILE: 14.216.02
FIRST VSAPI PATTERN DATE: 27 Apr 2018
VSAPI OPR PATTERN File: 14.213.00
VSAPI OPR PATTERN Date: 28 Apr 2018

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

Identify and terminate files detected as RANSOM_SEQUR.THDBGAH

[ Learn More ]
  1. Windows Task Manager may not display all running processes. In this case, please use a third-party process viewer, preferably Process Explorer, to terminate the malware/grayware/spyware file. You may download the said tool here.
  2. If the detected file is displayed in either Windows Task Manager or Process Explorer but you cannot delete it, restart your computer in safe mode. To do this, refer to this link for the complete steps.
  3. If the detected file is not displayed in either Windows Task Manager or Process Explorer, continue doing the next steps.

Step 4

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.  
  • {Folder with affected files}\HOW DECRIPT FILES.hta
  • %Start Menu%\Programs\Startup\HOW DECRIPT FILES.hta
  • %Desktop%\{generated random 40-letter string}.txt

Step 5

Scan your computer with your Trend Micro product to delete files detected as RANSOM_SEQUR.THDBGAH. 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 the following Trend Micro Support pages for more information:

Step 6

Restore encrypted files from backup.


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