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TROJ_PACKED.AYW

April 27, 2011
 Analysis by: Karl Dominguez
 ALIASES:

Mal/EncPk-EK ( Sophos); Trojan.Packed.NsAnti (Symantex); TrojanDownloader:Win32/Frethog.C (Microsoft)

 PLATFORM:

Windows 2000, Windows XP, Windows Server 2003

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

  • Threat Type: Trojan

  • Destructiveness: No

  • Encrypted: Yes

  • In the wild: Yes

  OVERVIEW

This Trojan may be dropped by other malware.

It requires its main component to successfully perform its intended routine.

  TECHNICAL DETAILS

File Size:

86,528 bytes

File Type:

DLL

Initial Samples Received Date:

29 Nov 2008

Payload:

Connects to URLs/Ips, Downloads files, Modifies system registry

Arrival Details

This Trojan may be dropped by other malware.

Installation

This Trojan is injected into the following processes running in memory:

  • Explorer.exe

Other System Modifications

This Trojan adds the following registry keys:

HKEY_CLASSES_ROOT\CLSID\MADOWN

It adds the following registry entries:

HKEY_CLASSES_ROOT\CLSID\MADOWN
urlinfo = "{random characters}"

It modifies the following registry entries:

HKEY_CURRENT_USER\Software\Microsoft\
Windows\CurrentVersion\Explorer\
Advanced
Hidden = "2"

(Note: The default value data of the said registry entry is 1.)

HKEY_CURRENT_USER\Software\Microsoft\
Windows\CurrentVersion\Explorer\
Advanced
ShowSuperHidden = "0"

(Note: The default value data of the said registry entry is 1.)

HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\
Windows\CurrentVersion\Explorer\
Advanced\Folder\Hidden\
SHOWALL
CheckedValue = "0"

(Note: The default value data of the said registry entry is 1.)

Download Routine

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

  • http://www.{BLOCKED}w.com/rbv/uu.rar

Other Details

This Trojan requires its main component to successfully perform its intended routine.

  SOLUTION

Minimum Scan Engine:

8.900

FIRST VSAPI PATTERN FILE:

5.682.18

FIRST VSAPI PATTERN DATE:

29 Nov 2008

Step 1

For Windows ME and XP users, before doing any scans, please make sure you disable System Restore to allow full scanning of your computer.

Step 2

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_CLASSES_ROOT\CLSID
    • MADOWN

Step 3

Restore this modified 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\Explorer\Advanced 
    • From Hidden = 2
      To: Hidden = 1
  • In HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\Explorer\Advanced
    • From: ShowSuperHidden = 0
      To: ShowSuperHidden = 1
  • In HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion\Explorer\Advanced\Folder\Hidden\SHOWALL
    • From: CheckedValue = 0
      To: CheckedValue = 1

Step 4

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