TROJ_DLDR.FX
Windows 2000, XP, Server 2003
Threat Type: Trojan
Destructiveness: No
Encrypted: No
In the wild: Yes
OVERVIEW
This Trojan may be dropped by other malware. It may be unknowingly downloaded by a user while visiting malicious websites. However, as of this writing, the said sites are inaccessible.
It executes the downloaded files. As a result, malicious routines of the downloaded files are exhibited on the affected system.
TECHNICAL DETAILS
Arrival Details
This Trojan may be dropped by other malware.
It may be unknowingly downloaded by a user while visiting malicious websites.
However, as of this writing, the said sites are inaccessible.
Installation
This Trojan is injected into the following processes running in memory:
- EXPLORER.EXE
Autostart Technique
This Trojan adds the following registry entries to enable its automatic execution at every system startup:
HKEY_CLASSES_ROOT\CLSID\{1A7882DB-B89E-4406-AF8A-42C3DBD11B2C}\
InprocServer32
@ = {malware path and file name]
Other System Modifications
This Trojan adds the following registry keys as part of its installation routine:
HKEY_CLASSES_ROOT\Comhtml.mshtml
HKEY_CLASSES_ROOT\Comhtml.mshtml.1
HKEY_CLASSES_ROOT\CLSID\{1A7882DB-B89E-4406-AF8A-42C3DBD11B2C}
HKEY_CLASSES_ROOT\TypeLib\{B02DAAF7-C679-4D00-9805-BE94D23B3B99}
Download Routine
This Trojan then executes the downloaded files. As a result, malicious routines of the downloaded files are exhibited on the affected system.
Other Details
Based on analysis of the codes, it has the following capabilities:
- Upon execution, it gets the local time and connects to the website, http://{BLOCKED}e.idirectech.com/support.html when the day is Thursday and the time is above 9 AM (10 AM - 11 PM).
- Based on its code, the reply from the server is a script which contains strings. It then matches the strings to its list of strings to check the file to download.
SOLUTION
Step 1
For Windows XP and Windows Server 2003 users, before doing any scans, please make sure you disable System Restore to allow full scanning of your computer.
Step 2
Scan your computer with your Trend Micro product and note files detected as TROJ_DLDR.FX
Step 3
Restart in Safe Mode
Step 4
Delete this registry key
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. Before you could do this, you must restart in Safe Mode. For instructions on how to do this, you may refer to this page If the preceding step requires you to restart in safe mode, you may proceed to edit the system registry.
- In HKEY_CLASSES_ROOT
- Comhtml.mshtml
- Comhtml.mshtml
- In HKEY_CLASSES_ROOT
- Comhtml.mshtml.1
- Comhtml.mshtml.1
- In HKEY_CLASSES_ROOT\CLSID
- {1A7882DB-B89E-4406-AF8A-42C3DBD11B2C}
- {1A7882DB-B89E-4406-AF8A-42C3DBD11B2C}
- In HKEY_CLASSES_ROOT\TypeLib
- {B02DAAF7-C679-4D00-9805-BE94D23B3B99}
- {B02DAAF7-C679-4D00-9805-BE94D23B3B99}
Step 5
Search and delete the file detected as TROJ_DLDR.FX
Step 6
Scan your computer with your Trend Micro product to delete files detected as TROJ_DLDR.FX. 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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