Analysis by: Julie Anne Cabuhat
ALIASES:

Trojan.Win32.Agent.neydao (Kaspersky), Trojan.MSIL.Filecoder (Ikarus)

 PLATFORM:

Windows

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

  • Threat Type: Trojan

  • Destructiveness: No

  • Encrypted: No

  • In the wild: Yes

  OVERVIEW

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

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.

  TECHNICAL DETAILS

File Size: 563,712 bytes
File Type: EXE
Memory Resident: Yes
Initial Samples Received Date: 27 Nov 2016
Payload: Encrypts 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.

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
Crypt = %User Startup%\HTCryptor.exe

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

  • %User Startup%\HTCryptor.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.)

Dropping Routine

This Trojan drops the following files:

  • %User Startup%\HTDecryptor.exe - Decryptor Module
  • %Desktop%\HTDecryptor.exe - Decryptor Module
  • %Start Menu%\HTDecryptor.exe - Decryptor Module
  • %Program Files%\HTDecryptor.exe - Decryptor Module
  • %User Profile%\Videos\Decryptor.exe - Decryptor Module
  • %User Profile%\Pictures\HTDecryptor.exe - Decryptor Module
  • %User Profile%\Music\HTDecryptor.exe - Decryptor Module
  • %User Startup%\message.exe - lock screen message

(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.. %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.. %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.. %Program Files% is the Program Files folder, where it usually is C:\Program Files on all Windows operating system versions; C:\Program Files (x86) for 32-bit applications running on Windows 64-bit operating systems.. %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.)

Other Details

This Trojan connects to the following URL(s) to check for an Internet connection:

  • http://www.websitetest.com/

It encrypts files with the following extensions:

  • .txt
  • .doc
  • .docx
  • .log
  • .msg
  • .odt
  • .pages
  • .rtf
  • .tex
  • .wpd
  • .wps
  • .csv
  • .dat
  • .ged
  • .key
  • .keychain
  • .pps
  • .ppt
  • .pptx
  • .sdf
  • .tar
  • .tax2014
  • .tax2015
  • .vcf
  • .xml
  • .aif
  • .iff
  • .m3u
  • .m4a
  • .mid
  • .mp3
  • .mpa
  • .wav
  • .wma
  • .3g2
  • .3gp
  • .asf
  • .avi
  • .flv
  • .m4v
  • .mov
  • .mp4
  • .mpg
  • .rm
  • .srt
  • .swf
  • .vob
  • .wmv
  • .3dm
  • .3ds
  • .max
  • .obj
  • .bmp
  • .dds
  • .gif
  • .jpg
  • .png
  • .psd
  • .tga
  • .thm
  • .tif
  • .tiff
  • .yuv
  • .ai
  • .eps
  • .ps
  • .svg
  • .indd
  • .pct
  • .pdf
  • .xlr
  • .xls
  • .xlsx
  • .accdb
  • .db
  • .dbf
  • .mdb
  • .pdb
  • .sql
  • .dwg
  • .dxf
  • .asp
  • .aspx
  • .cer
  • .cfm
  • .csr
  • .css
  • .htm
  • .html
  • .js
  • .jsp
  • .php
  • .rss
  • .xhtml
  • .7z
  • .cbr
  • .deb
  • .gz
  • .pkg
  • .rar
  • .rpm
  • .sitx
  • .tar.gz
  • .zip
  • .zipx
  • .bin
  • .cue
  • .dmg
  • .iso
  • .mdf
  • .toast
  • .vcd
  • .class
  • .cpp
  • .cs
  • .dtd
  • .fla
  • .java
  • .lua
  • .pl
  • .py
  • .sh
  • .sln
  • .swift
  • .vb
  • .vcxproj
  • .xcodeproj
  • .bak
  • .tmp
  • .crdownload
  • .ics
  • .msi
  • .part
  • .torrent

It renames encrypted files using the following names:

  • {Original filename and extension}.locked

It does the following:

  • It disables the firewall using the following command:
    • netsh firewall set opmode disable

NOTES:

The ransomware displays the following lock screen:

The ransomware displays the following window as its decryptor module:

  SOLUTION

Minimum Scan Engine: 9.850
FIRST VSAPI PATTERN FILE: 12.928.06
FIRST VSAPI PATTERN DATE: 29 Nov 2016
VSAPI OPR PATTERN File: 12.929.00
VSAPI OPR PATTERN Date: 30 Nov 2016

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

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
    • Crypt = "%User Startup%\HTCryptor.exe"

Step 5

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.
  • %User Startup%\HTDecryptor.exe
  • %Desktop%\HTDecryptor.exe
  • %Start Menu%\HTDecryptor.exe
  • %Program Files%\HTDecryptor.exe
  • %User Profile%\Videos\Decryptor.exe
  • %User Profile%\Pictures\HTDecryptor.exe
  • %User Profile%\Music\HTDecryptor.exe
  • %User Startup%\message.exe

Step 6

Restart in normal mode and scan your computer with your Trend Micro product for files detected as RANSOM_HIDDENTEARDECRYPTOR.A. 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 encrypted files from backup.

NOTES:

Enable disabled firewall using the following command prompt:

  • netsh firewall set opmode enable


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