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TROJ_FAKEAV.YSUZ

March 29, 2014
 PLATFORM:

Windows 2000, Windows XP, Windows Server 2003

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

  • Threat Type: Trojan

  • Destructiveness: No

  • Encrypted:

  • In the wild: Yes

  OVERVIEW


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.

  TECHNICAL DETAILS

File Size:

884,736 bytes

File Type:

EXE

Memory Resident:

Yes

Initial Samples Received Date:

29 Mar 2014

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 creates the following folders:

  • %User Profile%\Application Data\7hn36l33

(Note: %User Profile% is the current user's profile folder, which is usually C:\Documents and Settings\{user name} on Windows 2000, XP, and Server 2003, or C:\Users\{user name} on Windows Vista and 7.)

Autostart Technique

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

HKEY_CURRENT_USER\Software\Microsoft\
Windows\CurrentVersion\Run
AS2014 = "%User Profile%\7hn36l33\7hn36l33.exe"

Other System Modifications

This Trojan modifies the following file(s):

  • %Application Data%\GDIPFONTCACHEV1.DAT

(Note: %Application Data% is the current user's Application Data folder, which is usually C:\Documents and Settings\{user name}\Application Data on Windows 2000, XP, and Server 2003, or C:\Users\{user name}\AppData\Roaming on Windows Vista and 7.)

It modifies the following registry entries:

HKEY_CURRENT_USER\Software\Microsoft\
GDIPlus
FontCachePath = "%Application Data%"

(Note: The default value data of the said registry entry is %User Profile%\Local Settings\Application Data.)

Dropping Routine

This Trojan drops the following files:

  • %User Profile%\7hn36l33\7hn36l33.exe
  • %User Profile%\7hn36l33\7hn36l33axaQsaag.in
  • %User Profile%\7hn36l33\7hn36l33axaQsaag.lg
  • %User Profile%\7hn36l33\7hn36l33.exe.manifest
  • %User Profile%\7hn36l33\7hn36l33.ico
  • %User Profile%\7hn36l33\DD2
  • %User Profile%\7hn36l33\DD1
  • %User Profile%\7hn36l33\DD3

(Note: %User Profile% is the current user's profile folder, which is usually C:\Documents and Settings\{user name} on Windows 2000, XP, and Server 2003, or C:\Users\{user name} on Windows Vista and 7.)

Other Details

This Trojan connects to the following possibly malicious URL:

  • http://{BLOCKED}2.3.97/api/dom/no_respond/?{random characters}
  • http://{BLOCKED}2.3.97/api/stats/debug/2/?{random characters}
  • http://{BLOCKED}2.3.97/api/stats/debug/1/?{random characters}
  • http://{BLOCKED}2.3.97/api/stats/debug/3/?{random characters}

This report is generated via an automated analysis system.

  SOLUTION

Minimum Scan Engine:

9.300

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

Restart in Safe Mode

[ Learn More ]

Step 3

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_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\Run
    • AS2014 = "%User Profile%\7hn36l33\7hn36l33.exe"

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\Software\Microsoft\GDIPlus
    • From: FontCachePath = "%Application Data%"
      To: FontCachePath = ""%User Profile%\Local Settings\Application Data""

Step 5

Search and delete these components

[ Learn More ]
There may be some components 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 Profile%\7hn36l33\7hn36l33.exe
  • %User Profile%\7hn36l33\7hn36l33axaQsaag.in
  • %User Profile%\7hn36l33\7hn36l33axaQsaag.lg
  • %User Profile%\7hn36l33\7hn36l33.exe.manifest
  • %User Profile%\7hn36l33\7hn36l33.ico
  • %User Profile%\7hn36l33\DD2
  • %User Profile%\7hn36l33\DD1
  • %User Profile%\7hn36l33\DD3

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.
  • %User Profile%\Application Data\7hn36l33

Step 7

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

Restore deleted/modified files and/or registry entries from backup

*Note: Only Microsoft-related files/keys/values will be restored. If this malware/grayware also deleted registry keys/values related to programs that are not from Microsoft, please reinstall those programs on your computer.

    • %Application Data%\GDIPFONTCACHEV1.DAT


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