Analysis by: Francis Xavier Antazo
 Modified by: Cris Nowell Pantanilla
ALIASES:

Trojan.Win32.Agent.nexhgu (Kaspersky)

 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: Spammed via email

This Trojan arrives as an attachment to email messages spammed by other malware/grayware or malicious users.

It uses Windows Task Scheduler to create a scheduled task that executes the dropped copy.

  TECHNICAL DETAILS

File Size: 593,920 bytes
File Type: EXE
Memory Resident: Yes
Initial Samples Received Date: 19 Sep 2016
Payload: Encrypts files, Displays graphics/image

Arrival Details

This Trojan arrives as an attachment to email messages spammed by other malware/grayware or malicious users.

Installation

This Trojan drops the following files:

  • %User Profile%\My Documents\!!! Readme For Decrypt !!!.txt (ransom note)
  • %Desktop%\ReadMeFilesDecrypt!!!.txt (ransom note)

(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.)

It drops the following copies of itself into the affected system:

  • %All Users Profile%\Documents\My Music\{RANDOM STRING}.exe
  • %All Users Profile%\Documents\My Pictures\{RANDOM STRING}.exe
  • %All Users Profile%\Documents\My Videos\{RANDOM STRING}.exe
  • %All Users Profile%\Documents\{RANDOM STRING}.exe
  • %User Profile%\My Documents\My Music\{RANDOM STRING}.exe
  • %User Profile%\My Documents\{RANDOM STRING}.exe

(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.. %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 uses Windows Task Scheduler to create a scheduled task that executes the dropped copy.

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\RunOnce
{RANDOM STRING} = {malware executed path and filename}

HKEY_CURRENT_USER\Software\Microsoft\
Windows\CurrentVersion\RunOnce
{RANDOM STRING} = "%All Users Profile%\Documents\My Music\{RANDOM STRING}.exe"

HKEY_CURRENT_USER\Software\Microsoft\
Windows\CurrentVersion\RunOnce
{RANDOM STRING} = "%All Users Profile%\Documents\My Pictures\{RANDOM STRING}.exe"

HKEY_CURRENT_USER\Software\Microsoft\
Windows\CurrentVersion\RunOnce
{RANDOM STRING} = "%All Users Profile%\Documents\My Videos\{RANDOM STRING}.exe"

HKEY_CURRENT_USER\Software\Microsoft\
Windows\CurrentVersion\RunOnce
{RANDOM STRING} = "%All Users Profile%\Documents\{RANDOM STRING}.exe"

HKEY_CURRENT_USER\Software\Microsoft\
Windows\CurrentVersion\RunOnce
{RANDOM STRING} = "%User Profile%\My Documents\My Music\{RANDOM STRING}.exe"

HKEY_CURRENT_USER\Software\Microsoft\
Windows\CurrentVersion\RunOnce
{RANDOM STRING} = "%User Profile%\My Documents\{RANDOM STRING}.exe"

HKEY_CURRENT_USER\Software\Microsoft\
Windows\CurrentVersion\Run
{RANDOM STRING} = {malware executed path and filename}

HKEY_CURRENT_USER\Software\Microsoft\
Windows\CurrentVersion\Run
{RANDOM STRING} = "%All Users Profile%\Documents\My Music\{RANDOM STRING}.exe"

HKEY_CURRENT_USER\Software\Microsoft\
Windows\CurrentVersion\Run
{RANDOM STRING} = "%All Users Profile%\Documents\My Pictures\{RANDOM STRING}.exe"

HKEY_CURRENT_USER\Software\Microsoft\
Windows\CurrentVersion\Run
{RANDOM STRING} = "%All Users Profile%\Documents\My Videos\{RANDOM STRING}.exe"

HKEY_CURRENT_USER\Software\Microsoft\
Windows\CurrentVersion\Run
{RANDOM STRING} = "%All Users Profile%\Documents\{RANDOM STRING}.exe"

HKEY_CURRENT_USER\Software\Microsoft\
Windows\CurrentVersion\Run
{RANDOM STRING} = "%User Profile%\My Documents\My Music\{RANDOM STRING}.exe"

HKEY_CURRENT_USER\Software\Microsoft\
Windows\CurrentVersion\Run
{RANDOM STRING} = "%User Profile%\My Documents\{RANDOM STRING}.exe"

It enables its automatic execution at every system startup by dropping the following copies of itself into the Windows Common Startup folder:

  • %All Users Profile%\Start Menu\Programs\Startup\{RANDOM STRING}.exe

(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.)

Other System Modifications

This Trojan sets the system's desktop wallpaper to the following image:

Other Details

This Trojan encrypts files with the following extensions:

  • .1cd
  • .3ds
  • .3fr
  • .3pr
  • .ab4
  • .ac2
  • .accdb
  • .accde
  • .accdr
  • .accdt
  • .acr
  • .adb
  • .agd1
  • .ait
  • .apj
  • .arw
  • .asm
  • .asp
  • .awg
  • .backup
  • .backupdb
  • .bak
  • .bdb
  • .bgt
  • .bik
  • .bkp
  • .blend
  • .bpw
  • .cdf
  • .cdr
  • .cdr3
  • .cdr4
  • .cdr5
  • .cdr6
  • .cdrw
  • .cdx
  • .ce1
  • .ce2
  • .cer
  • .cfp
  • .cgm
  • .cib
  • .cls
  • .cmt
  • .cpi
  • .cpp
  • .cr2
  • .craw
  • .crt
  • .crw
  • .csh
  • .csl
  • .css
  • .csv
  • .dac
  • .db-journal
  • .db3
  • .dbf
  • .dc2
  • .dcr
  • .dcs
  • .ddd
  • .ddoc
  • .ddrw
  • .der
  • .design
  • .dgc
  • .djvu
  • .dng
  • .doc
  • .docm
  • .docx
  • .dot
  • .dotm
  • .dotx
  • .drf
  • .drw
  • .dwg
  • .dxb
  • .epf
  • .erbsql
  • .erf
  • .ert
  • .exf
  • .fdb
  • .ffd
  • .fff
  • .fhd
  • .fpx
  • .fxg
  • .gray
  • .grey
  • .gry
  • .hbk
  • .hpp
  • .ibank
  • .ibd
  • .ibz
  • .idx
  • .iiq
  • .incpas
  • .jpeg
  • .jpg
  • .kc2
  • .kdbx
  • .kdc
  • .kpdx
  • .lua
  • .mdb
  • .mdc
  • .mef
  • .mfw
  • .mmw
  • .moneywell
  • .mos
  • .mpg
  • .mrw
  • .myd
  • .ndd
  • .nef
  • .nop
  • .nrw
  • .ns2
  • .ns3
  • .ns4
  • .nsd
  • .nsf
  • .nsg
  • .nsh
  • .nwb
  • .nx1
  • .nx2
  • .nyf
  • .odb
  • .odf
  • .odg
  • .odm
  • .odp
  • .ods
  • .odt
  • .orf
  • .otg
  • .oth
  • .otp
  • .ots
  • .ott
  • .p12
  • .p7b
  • .pat
  • .pcd
  • .pdf
  • .pef
  • .pem
  • .pfx
  • .php
  • .pot
  • .potm
  • .potx
  • .ppam
  • .pps
  • .ppsm
  • .ppsx
  • .ppt
  • .pptm
  • .pptx
  • .psafe3
  • .psd
  • .ptx
  • .ra2
  • .raf
  • .rar
  • .raw
  • .rdb
  • .rtf
  • .rw2
  • .rwl
  • .rwz
  • .s3db
  • .sas7bdat
  • .sav
  • .sd0
  • .sd1
  • .sda
  • .sdf
  • .sldm
  • .sldx
  • .sql
  • .sqlite
  • .sqlite3
  • .sqlitedb
  • .sr2
  • .srf
  • .srw
  • .st4
  • .st5
  • .st6
  • .st7
  • .st8
  • .stc
  • .std
  • .sti
  • .stw
  • .stx
  • .sxc
  • .sxd
  • .sxg
  • .sxi
  • .sxm
  • .sxw
  • .txt
  • .wb2
  • .x3f
  • .xla
  • .xlam
  • .xll
  • .xlm
  • .xls
  • .xlsb
  • .xlsm
  • .xlsx
  • .xlt
  • .xltm
  • .xltx
  • .xlw
  • .xml
  • .ycbcra
  • .zip

NOTES:

It adds the following mutex to ensure that only one of its copies runs at any one time: HelloWorldItsJokeFromMars

It writes the following string at the start of encrypted files: HUI

This ransomware drops the following ransom note:

  SOLUTION

Minimum Scan Engine: 9.800
FIRST VSAPI PATTERN FILE: 12.786.08
FIRST VSAPI PATTERN DATE: 19 Sep 2016
VSAPI OPR PATTERN File: 12.787.00
VSAPI OPR PATTERN Date: 20 Sep 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

Restart in Safe Mode

[ Learn More ]

Step 3

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\RunOnce
    • {RANDOM STRING} = {malware executed path and filename}
  • In HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\RunOnce
    • {RANDOM STRING} = "%All Users Profile%\Documents\My Music\{RANDOM STRING}.exe"
  • In HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\RunOnce
    • {RANDOM STRING} = "%All Users Profile%\Documents\My Pictures\{RANDOM STRING}.exe"
  • In HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\RunOnce
    • {RANDOM STRING} = "%All Users Profile%\Documents\My Videos\{RANDOM STRING}.exe"
  • In HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\RunOnce
    • {RANDOM STRING} = "%All Users Profile%\Documents\{RANDOM STRING}.exe"
  • In HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\RunOnce
    • {RANDOM STRING} = "%User Profile%\My Documents\My Music\{RANDOM STRING}.exe"
  • In HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\RunOnce
    • {RANDOM STRING} = "%User Profile%\My Documents\{RANDOM STRING}.exe"
  • In HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\Run
    • {RANDOM STRING} = {malware executed path and filename}
  • In HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\Run
    • {RANDOM STRING} = "%All Users Profile%\Documents\My Music\{RANDOM STRING}.exe"
  • In HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\Run
    • {RANDOM STRING} = "%All Users Profile%\Documents\My Pictures\{RANDOM STRING}.exe"
  • In HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\Run
    • {RANDOM STRING} = "%All Users Profile%\Documents\My Videos\{RANDOM STRING}.exe"
  • In HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\Run
    • {RANDOM STRING} = "%All Users Profile%\Documents\{RANDOM STRING}.exe"
  • In HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\Run
    • {RANDOM STRING} = "%User Profile%\My Documents\My Music\{RANDOM STRING}.exe"
  • In HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\Run
    • {RANDOM STRING} = "%User Profile%\My Documents\{RANDOM STRING}.exe"

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.
%User Profile%\My Documents\!!! Readme For Decrypt !!!.txt
%Desktop%\ReadMeFilesDecrypt!!!.txt

Step 5

Restart in normal mode and scan your computer with your Trend Micro product for files detected as RANSOM_JOKEMARS.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 6

Restore encrypted files from backup.

Step 7

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


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