Classification

Category :

Malware

Type :

Worm

Aliases :

Webber, TrojanProxy.Win32.Webber, W32/Heloc-mm

Summary

UPDATE (2003-07-22 7:15 GMT)

Another variant has been discovered, the email messages used on this occasion have the following format:

From:
 Wells Fargo Accounting [wfba.accounting@wellsfargo.com]

Subject:
 
Re: Wells Fargo Bank New Business Account Application - ID# 4489

Body:

Dear Sir,
 
Thank you for your online application for a Business Account with Wells
Fargo. We appreciate your interest in banking with us.
 
In order to open a Business Account, we must receive specific credit
information that is verifiable. Because Wells Fargo has no locations in
your state, we are unable to confirm the credit information in your
application. Consequently, we regret to say that we cannot open an
account for your business at this time.

Attached are your Wells Fargo Application and your Social Security File.Sincerely,Sherli Chin

Business Resource Center Services

Wells Fargo Bank
 

UPDATE (2003-07-17 12:00 GMT)

A new variant of the downloader has been discovered. The email message it is received in has the following format:

Subject:
 Re: Your E-Loan Refinance Application
 
Body:
 
Dear sir,

 
Thank you for your recent online Refinance Application with E-Loan Inc.
Apparently you have moved from your current home address a couple of months
ago, so we coulnd't verify your identity with Credit Bureaus and Chexsystems.

We are sorry for any inconvenience.

 
Attached are scanned copies of your Home Value, Grant Deeds and your current
Credit Profile from 3 major Credit Bureaus. Take a close look at it, as you
will receive hard copies by usps mail in few days. 

The attachment name is "E-Loan-Appraiser-Results.pif". As of this writing, we don't have notice of this downloader being received in messages with a different content.

Removal

Based on the settings of your F-Secure security product, it will either move the file to the quarantine where it cannot spread or cause harm, or remove it.

A False Positive is when a file is incorrectly detected as harmful, usually because its code or behavior resembles known harmful programs. A False Positive will usually be fixed in a subsequent database update without any action needed on your part. If you wish, you may also:

  • Check for the latest database updates

    First check if your F-Secure security program is using the latest updates, then try scanning the file again.

  • Submit a sample

    After checking, if you still believe the file is incorrectly detected, you can submit a sample of it for re-analysis.

    Note: If the file was moved to quarantine, you need to collect the file from quarantine before you can submit it.

  • Exclude a file from further scanning

    If you are certain that the file is safe and want to continue using it, you can exclude it from further scanning by the F-Secure security product.

    Note: You need administrative rights to change the settings.

Technical Details

This trojan was mass-mailed on July 16 2003. The message arrived with an attachment containing the downloading component named "web.da.us.citi.heloc.pif".

The messages characteristics are:

Subject:
 Re: Your credit application

Body:
 
Dear sir,Thank you for your online application for a Citibank Home Equity Loan.
In order to be approved for any loan application we pull your Credit Profile
and Chexsystems information, which didn't satisfy our minimum needs.

Consequently, we regret to say that we cannot approve you for Citibank Home
Equity Loan at this time.*Attached are copy of your Credit Profile and Your Application that you
submitted with us. Please take a close look at it, you will receive hard copy
by mail withing next few days.
 

The attachment, once executed, downloads and installs a hidden proxy server which, in turn, creates an additional DLL. So the trojan has three components:

EXE downloader (5664 bytes of size)

EXE trojan (39140 bytes of size)

DLL component (5633 bytes of size)
 

The main component copies itself to Windows system directory with a randomly selected name and drops the DLL component with a randomly composed name as well.

The trojan does not register itself in any auto-run registry key or Windows INI files. The mechanism used by the worm to be executed relies on modifying the following registry keys:

HKCR\CLSID\{79FA9088-19CE-715D-D85A-216290C5B738}

InProcServer32 = %trojan DLL name%

ThreadingModel = Apartment
 
HKLM\Software\Microsoft\Windows\CurrentVersion\ShellServiceObjectDelayLoad

Web Event Logger = {79FA9088-19CE-715D-D85A-216290C5B738}
 

As a result on according events the trojan DLL file will be activated. The DLL seems to be responsible then, of executing the main binary.

This main executable is a proxy which will listen on the victim machine (up to 100 connections) and report the IP address of the infected machine and cached passwords to a hard-coded URL. The trojan also downloads from an URL and executes other EXE files.