Analysis by: Miguel Carlo Ang
ALIASES:

TrojanDownloader:Win32/Dalexis.F(Microsoft);Trojan-Downloader.Win32.Cabby.cgbx(Kaspersky);Downloader-CTB(McAfee)

 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 executes the downloaded files. As a result, malicious routines of the downloaded files are exhibited on the affected system.

  TECHNICAL DETAILS

File Size: 102,400 bytes
File Type: EXE
Memory Resident: No
Initial Samples Received Date: 30 Apr 2015
Payload: Connects to URLs/IPs

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 non-malicious files:

  • %User Temp%\{random 1}.cab
  • %User Temp%\FC00C0335EC892CF4E256B5F313B33E9D52ECBD5.rtf

(Note: %User Temp% is the user's temporary folder, where it usually is C:\Documents and Settings\{user name}\Local Settings\Temp on Windows 2000, Windows Server 2003, and Windows XP (32- and 64-bit); C:\Users\{user name}\AppData\Local\Temp 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:

  • pqgjiiaa

Download Routine

This Trojan connects to the following website(s) to download and execute a malicious file:

  • {BLOCKED}adiamonds.com/language/run.jpg
  • www.{BLOCKED}nico74.it/random/run.jpg
  • {BLOCKED}a.hr/files/run.jpg
  • {BLOCKED}ool.net/modules/run.jpg
  • {BLOCKED}romspace.{BLOCKED}6.com/run.jpg
  • {BLOCKED}l.{BLOCKED}6.net/run.jpg
  • {BLOCKED}oscreens.com/js/run.jpg

It saves the files it downloads using the following names:

  • %User Temp%\{random 2}.exe (TROJ_CRYPCTB.CD)

(Note: %User Temp% is the user's temporary folder, where it usually is C:\Documents and Settings\{user name}\Local Settings\Temp on Windows 2000, Windows Server 2003, and Windows XP (32- and 64-bit); C:\Users\{user name}\AppData\Local\Temp 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 then executes the downloaded files. As a result, malicious routines of the downloaded files are exhibited on the affected system.

Other Details

This Trojan opens the following files:

  • %User Temp%\FC00C0335EC892CF4E256B5F313B33E9D52ECBD5.rtf

(Note: %User Temp% is the user's temporary folder, where it usually is C:\Documents and Settings\{user name}\Local Settings\Temp on Windows 2000, Windows Server 2003, and Windows XP (32- and 64-bit); C:\Users\{user name}\AppData\Local\Temp 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.)

  SOLUTION

Minimum Scan Engine: 9.750
FIRST VSAPI PATTERN FILE: 11.666.05
FIRST VSAPI PATTERN DATE: 29 Apr 2015
VSAPI OPR PATTERN File: 11.667.00
VSAPI OPR PATTERN Date: 30 Apr 2015

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

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.
  • %User Temp%\{random 1}.cab
  • %User Temp%\FC00C0335EC892CF4E256B5F313B33E9D52ECBD5.rtf

Step 4

Remove malware/grayware files dropped/downloaded by TROJ_DALEXIS.YWI. (Note: Please skip this step if the threats listed below have already been removed.)

     TROJ_CRYPCTB.CD

Step 5

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