Analysis by: Joachim Suico
ALIASES:

Trojan-Downloader.HTML.Agent.aba (Kaspersky); Exploit:VBS/Phel.L (Microsoft); Trojan.Downloader.CHMall.C (F-Secure)

 PLATFORM:

Windows

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

  • Threat Type: Trojan

  • Destructiveness: No

  • Encrypted: No

  • In the wild:

  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.

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

  TECHNICAL DETAILS

File Size: 10,864 bytes
File Type: CHM
Memory Resident: No
Initial Samples Received Date: 03 Mar 2015
Payload: Connects to URLs/IPs, Downloads 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 and executes the following files:

  • {Malware Path}\tt.vbs

Download Routine

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

  • www.{BLOCKED}ire.com/tmp/tv.exe

It saves the files it downloads using the following names:

  • {Malware Path}\t.exe

Other Details

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

  SOLUTION

Minimum Scan Engine: 9.750
FIRST VSAPI PATTERN FILE: 11.522.07
FIRST VSAPI PATTERN DATE: 03 Mar 2015
VSAPI OPR PATTERN File: 11.523.00
VSAPI OPR PATTERN Date: 04 Mar 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.  
  • {Malware Path}\tt.vbs
  • {Malware Path}\t.exe

Step 4

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

*Note: 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 5

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