Summary

UPDATE (2003-07-22 7:15 GMT) Another variant has been discovered, the e-mail 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 e-mail 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.

Additional 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.



F-Secure Anti-Virus detects Webber worm with the updates published on July 16th, 2003:

Version=2003-07-16_03

[Analysis: Kaspersky Labs and F-Secure Corp.; July 16th, 2003]