Win32/Gibe.A is an email worm. This worm will infect Windows systems.

The worm arrives in an email as if it is an update coming from Microsoft.

It arrives with the following subject:

Internet Security Update

The body of the mail contains:

Microsoft Customer,

this is the latest version of security update, the update which eliminates all known security vulnerabilities affecting Internet Explorer and MS Outlook/Express as well as six new vulnerabilities, and is discussed in Microsoft Security Bulletin MS02-005. Install now to protect your computer from these vulnerabilities, the most serious of which could allow an attacker to run code on your computer.

Description of several well-know vulnerabilities:

- "Incorrect MIME Header Can Cause IE to Execute E-mail Attachment" vulnerability. If a malicious user sends an affected HTML e-mail or hosts an affected e-mail on a Web site, and a user opens the e-mail or visits the Web site, Internet Explorer automatically runs the executable on the user's computer.

- A vulnerability that could allow an unauthorized user to learn the location of cached content on your computer. This could enable the unauthorized user to launch compiled HTML Help (.chm) files that contain shortcuts to executables, thereby enabling the unauthorized user to run the executables on your computer.

- A new variant of the "Frame Domain Verification" vulnerability could enable a malicious Web site operator to open two browser windows, one in the Web site's domain and the other on your local file system, and to pass information from your computer to the Web site.

- CLSID extension vulnerability. Attachments which end with a CLSID file extension do not show the actual full extension of the file when saved and viewed with Windows Explorer. This allows dangerous file types to look as though they are simple, harmless files - such as JPG or WAV files - that do not need to be blocked.

System requirements:
Versions of Windows no earlier than Windows 95.

This update applies to:
Versions of Internet Explorer no earlier than 4.01
Versions of MS Outlook no earlier than 8.00
Versions of MS Outlook Express no earlier than 4.01

How to install
Run attached file q216309.exe

How to use
You don't need to do anything after installing this item.

For more information about these issues, read Microsoft Security Bulletin MS02-005, or visit link below. http://www.microsoft.com/windows/ie/downloads/critical/default.asp If you have some questions about this article contact us at rdquest12@microsoft.com

Thank you for using Microsoft products.

With friendly greetings,
MS Internet Security Center.
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Microsoft is registered trademark of Microsoft Corporation.
Windows and Outlook are trademarks of Microsoft Corporation.

The mail body indicates that the attachment carries a Microsoft Security Update attachment, q216309.exe. Upon execution of the attachment, it displays a message box with the following contents:

This will install Microsoft Security Update.
Do you wish to continue?

The message box contains Yes and No buttons. On selecting any one of these buttons, the worm drops itself into Windows system directory as Vtnmsccd.dll and MSWinsck.ocx. It also drops files under Windows directory as Q216309.exe, BcTool.exe, WinNetw.exe and GfxAcc.exe. The worm collects email addresses by executing a file called WinNetw.exe and stores in a file 02_N803.DAT under Windows directory. Later on, it uses email addresses stored in 02_N803.DAT file to send worm mails by using default SMTP engine.

The worm makes necessary changes to registry at the following location to load itself at next system startup.

HKEY_LOCAL_MACHINE\Software\Microsoft\Windows\CurrentVersion\Run

This worm first appeared on 4th March 2002.

Other names of Win32/Gibe.A worm:

This worm is also known as I-worm.Gibe, W32/Gibe.