TROJ_CRYPOLLO.A

May 19, 2015
 Analysis by: Joachim Suico
 ALIASES:

rojan.Cryptolocker.S (Symantec); Trojan-Ransom.Win32.ElPolock.a (Kaspersky); Troj/LPoLock-A (Sophos); PowerShell/Filecoder.A (ESET-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:

Spammed via email, Downloaded from the Internet, Dropped by other malware

This Trojan arrives as an attachment to email messages spammed by other malware/grayware or malicious users. It arrives on a system as a file dropped by other malware or as a file downloaded unknowingly by users when visiting malicious sites.

It injects its dropped file/component to specific processes.

It connects to certain websites to send and receive information.

  TECHNICAL DETAILS

File Size:

3,084,890 bytes

File Type:

Script

Memory Resident:

Yes

Initial Samples Received Date:

15 May 2015

Payload:

Drops files, Encrypts files, Connects to URLs/IPs

Arrival Details

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

It 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 injects its dropped file/component to the following processes:

  • Explorer

Other System Modifications

This Trojan modifies the following registry entries:

HKEY_CURRENT_USER\Control Panel\Desktop
WallpaperStyle = "0"

(Note: The default value data of the said registry entry is {User Preferences}.)

HKEY_CURRENT_USER\Control Panel\Desktop
Wallpaper = "%System Root%\1\locked.bmp"

(Note: The default value data of the said registry entry is {User Preferences}.)

Dropping Routine

This Trojan drops the following files:

  • %System Root%\1\t.dll - detected as TROJ_CRYPOLLO.A
  • %System Root%\1\reflect.dll - detected as TROJ_CRYPOLLO.A
  • %System Root%\1\locked.bmp - new wallpaper of affected system
  • %Desktop%\qwer.html
  • %Desktop%\qwer2.html
  • %Desktop%\customer.id
  • %Desktop%\seckeys.DONOTDELETE
  • %Desktop%\encrypted.htm
  • %Desktop%\decrypted.htm

(Note: %System Root% is the Windows root folder, where it usually is C:\ on all Windows operating system versions.. %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 Trojan connects to the following website to send and receive information:

  • {BLOCKED}.{BLOCKED}.220.38

It encrypts files with the following extensions:

  • .ai
  • .crt
  • .csv
  • .db
  • .doc
  • .docm
  • .docx
  • .dotx
  • .gif
  • .jpeg
  • .jpg
  • .jpg
  • .lnk
  • .mp3
  • .msi
  • .ods
  • .one
  • .ost
  • .p12
  • .pdf
  • .pem
  • .pps
  • .ppsx
  • .ppt
  • .pptx
  • .psd
  • .pst
  • .pub
  • .rar
  • .raw
  • .rtf
  • .tif
  • .txt
  • .vsdx
  • .wma
  • .xls
  • .xlsm
  • .xlsx
  • .xml
  • .zip

NOTES:

It downloads and opens a non-malicious file from the following website:

  • http://www.{BLOCKED}l.sk.origin.dhl.com/content/dam/downloads/sk/logistics/Shipping%20conditions%20DHL%20Euroconnect%20Domestic%2022.02.pdf

The downloaded file is saved as {malware path}\penalty.pdf.

It also encrypts files located in network shares. The encrypted files have file names appended with .ha3.

It connects to a remote location to download PowerShell code:

  • http://{BLOCKED}.{BLOCKED}.220.38/wall/Invoke-ReflectivePEInjection.ps1

The malicious components that are injected into the Explorer process enables the execution of the following routines:

  • Deletes shadow copies
  • Disables System Restore
  • Disables Startup Repair

The malware demands ransom for the encrypted files:

It sets the wallpaper of the infected system into the following image:

It also connects to the following website to play music in the background:

  • https://www.youtube.com/watch?v=8zCpQZPX1IA

  SOLUTION

Minimum Scan Engine:

9.750

FIRST VSAPI PATTERN FILE:

11.670.07

FIRST VSAPI PATTERN DATE:

15 May 2015

VSAPI OPR PATTERN File:

11.671.00

VSAPI OPR PATTERN Date:

16 May 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

Restore these modified registry values

[ Learn More ]

Important:Editing the Windows Registry incorrectly can lead to irreversible system malfunction. Please do this only if you know how to or you can seek your system administrator's help. You may also check out this Microsoft article first before modifying your computer's registry.

  • In HKEY_CURRENT_USER\Control Panel\Desktop
    • From: WallpaperStyle = "0" To: {User Preferences}
  • In HKEY_CURRENT_USER\Control Panel\Desktop
    • From: Wallpaper = "%System Root%\1\locked.bmp" To: {User Preferences}

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.
  • %System Root%\1\locked.bmp
  • %Desktop%\qwer.html
  • %Desktop%\qwer2.html
  • %Desktop%\customer.id
  • %Desktop%\seckeys.DONOTDELETE
  • %Desktop%\encrypted.htm
  • %Desktop%\decrypted.htm
  • {malware path}\penalty.pdf

Step 6

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