RANSOM_CRYPTLOCK.AN

July 05, 2016
 Analysis by: Jennifer Gumban
 ALIASES:

Ransom:Win32/Teerac.F (Microsoft); Win32/Filecoder.TorrentLocker.A 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 connects to certain websites to send and receive information. However, as of this writing, the said sites are inaccessible.

  TECHNICAL DETAILS

File Size:

811,008 bytes

File Type:

EXE

Memory Resident:

Yes

Initial Samples Received Date:

14 Jun 2016

Payload:

Connects to URLs/IPs, 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.

Installation

This Trojan drops the following copies of itself into the affected system:

  • %Windows%\{random 8 letters}.exe

(Note: %Windows% is the Windows folder, where it usually is C:\Windows on all Windows operating system versions.)

It drops the following file(s)/component(s):

  • %All Users Profile%\Application Data\{random folder name}\{8 random letters}

(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.)

It adds the following processes:

  • explorer.exe

It creates the following folders:

  • %All Users Profile%\Application Data\{random folder name}

(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.)

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

  • Global\{random}

It injects codes into the following process(es):

  • created explorer.exe

Autostart Technique

This Trojan adds the following registry entries to enable its automatic execution at every system startup:

HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\
Windows\CurrentVersion\Run
{random letters} = "%Windows%\{random 8 letters}.exe"

Other System Modifications

This Trojan adds the following registry keys:

HKEY_CURRENT_USER\Software\Microsoft\
Internet Explorer\PhishingFilter

It adds the following registry entries:

HKEY_CURRENT_USER\Software\Microsoft\
Internet Explorer\PhishingFilter
EnabledV8 = 0

HKEY_CURRENT_USER\Software\Microsoft\
Internet Explorer\PhishingFilter
EnabledV9 = 0

Information Theft

This Trojan gathers the following data:

  • Machine GUID
  • Computer name

Other Details

This Trojan connects to the following URL(s) to get the affected system's IP address:

  • http://ipecho.net/plain

It connects to the following website to send and receive information:

  • https://{pseudo-random}.{BLOCKED}edy.org/topic.php
  • http://{BLOCKED}.{BLOCKED}.21.38:443

It encrypts files with the following extensions:

  • 3gp
  • aac
  • ans
  • ape
  • asc
  • asm
  • asp
  • aspx
  • avi
  • awk
  • bas
  • bat
  • bmp
  • c
  • cs
  • cls
  • clw
  • cmd
  • cpp
  • csproj
  • css
  • ctl
  • cxx
  • def
  • dep
  • dlg
  • dsp
  • dsw
  • eps
  • f
  • f77
  • f90
  • f95
  • fla
  • flac
  • frm
  • gif
  • h
  • hpp
  • hta
  • htm
  • html
  • hxx
  • ico
  • idl
  • inc
  • ini
  • inl
  • java
  • jpeg
  • jpg
  • js
  • la
  • mak
  • manifest
  • wmv
  • mov
  • mp3
  • mp4
  • mpe
  • mpeg
  • mpg
  • m4a
  • ofr
  • ogg
  • pac
  • pas
  • pdf
  • php
  • php3
  • php4
  • php5
  • phptml
  • pl
  • pm
  • png
  • ps
  • py
  • pyo
  • ra
  • rb
  • rc
  • reg
  • rka
  • rm
  • rtf
  • sed
  • sh
  • shn
  • shtml
  • sln
  • sql
  • srt
  • swa
  • tcl
  • tex
  • tiff
  • tta
  • txt
  • vb
  • vcproj
  • vbs
  • wa
  • v
  • wma
  • wv
  • xml
  • xsd
  • xsl
  • xslt

It renames encrypted files using the following names:

  • {original file name and extension}.encrypted

However, as of this writing, the said sites are inaccessible.

NOTES:

It deletes shadow copies by executing the following command:

  • vssadmin.exe Delete Shadows /All /Quiet

  SOLUTION

Minimum Scan Engine:

9.800

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_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion\Run
    • {random letters} = "%Windows%\{random 8 letters}.exe"

Step 5

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\Microsoft\Internet Explorer
    • PhishingFilter

Step 6

Search and delete this folder

[ Learn More ]
Please make sure you check the Search Hidden Files and Folders checkbox in the More advanced options option to include all hidden folders in the search result.
  • %All Users Profile%\Application Data\{random folder name}

Step 7

Restart in normal mode and scan your computer with your Trend Micro product for files detected as RANSOM_CRYPTLOCK.AN. 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 8

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