Name :	Warezov.W
Category:	Malware
Type:	Email-Worm
Platform:	W32
Date of Discovery:	September 12, 2006

Warezov.W is a mass-mailing worm that sends itself as e-mail attachments to addresses found on the infected computer.

Typically, a mass-mailer arrives on a computer with an infected e-mail message. In some cases, the infected attachment can start automatically. In other cases, the system is infected when the user opens the attachment. When a typical mass-mailer is activated, it installs itself to the system and creates a startup key for itself in the Windows registry. It then stays active in the system's memory. While active, the mass-mailer searches for specific files (HTML files for example) on all available hard disks for e-mail addresses. Finally, it connects to an available mail server and sends itself to all the addresses it has found.

Aside from this, Warezov.W also downloads another worm variant from a specified website on the Internet.

Automatic Disinfection

Usually standalone malware (backdoors, worms, trojans, etc.) is automatically removed by F-Secure Anti-Virus (FSAV) starting from version 5.40. Malware files get automatically renamed by FSAV, so they can not be started any more. In some rare cases, when automatic disinfection is not possible, a user can select disinfection action by him/herself to make FSAV rename or delete an infected file. In some special cases it is recommended to use specific disinfection tools provided by F-Secure. They can be downloaded from our ftp site:

ftp://ftp.f-secure.com/anti-virus/tools/

F-Secure Anti-Virus can be purchased from our webshop or from our authorised distributors. A trial version F-Secure Anti-Virus, limited to 30 days, can be downloaded from our website:

http://www.f-secure.com/download-purchase/

All the latest versions of FSAV can download anti-virus database updates automatically. However, these updates can be also downloaded and installed manually from our web or ftp sites:

http://www.f-secure.com/download-purchase/updates.shtml


Manual Disinfection

To manually disinfect standalone malware (backdoors, worms, trojans, etc.) it's usually enough to delete all infected files from a computer and to restart it. Active malware files are usually locked by operating system so different disinfection approaches are required for different operating systems.
Please note that manual disinfection is a risky process, so it is recommended only for advanced users.

If Windows 95, 98 and ME operating system is used, it is recommended to restart a computer from a bootable system diskette and to delete an infected file from command prompt. For example if a malicious file named ABC.EXE is located in Windows folder, it is usually enough to type the following command at command prompt:

DEL C:\WINDOWS\ABC.EXE

and to press Enter. After that an infected file will be gone. If Windows NT, 2000 or XP is used, a malicious file has to be renamed with a different extension (for example .VIR) and then a system has to be restarted. After restart a renamed malicious file will no longer be active and it can be easily deleted manually.


Malware Disinfection Tools

F-Secure provides disinfection tools for certain malware. These tools can be downloaded from this webpage:

http://www.f-secure.com/download-purchase/tools.shtml

ftp://ftp.f-secure.com/anti-virus/tools/


Windows System Restore Issues

If Windows ME or XP is used, it is recommended to disable System Restore feature of these operating systems to prevent a computer from re-infection by an already removed malware. The fact is that System Restore feature of these operating systems might save an infected file into the special folder and copy it back to a hard drive it every time it's been renamed or deleted by F-Secure Anti-Virus or by a user. Instructions on how to disable System Restore feature are here:

Windows ME:
http://www.f-secure.com/v-descs/sfc_dis.shtml

Windows XP:
http://www.f-secure.com/v-descs/sfc_dis1.shtml

It is recommended to re-enable System Restore after disinfection in order to restore stable system configuration in the future, if any crash or incompatibility issue occurs.


Failed Disinfection

In some cases F-Secure Anti-Virus might not disinfect a system automatically. In this case please visit our Support pages:

http://support.f-secure.com/enu/home/virusproblem/howtoclean/

Warezov.W is a mass-mailing worm that sends itself as e-mail attachments to addresses found on the infected computer. Below are example screenshots of this worm:






The worm shows this messagebox as a decoy during installation to a system:




To ensure its execution every system startup, Warezov.W creates the following registry launch points:


It adds these files:


The worm also copies the file it was run from to Windows System folder.


Warezov.W also modifies the Windows HOSTS file to prevent access to the following websites:



It gathers target e-mail addresses from the Windows Address Book (WAB). It may also harvests e-mail addresses from the infected system by scanning through files with the following extension names:



The worm filters found e-mail addresses to avoid sending itself to addresses that contain any of the following substrings:



The worm then sends itself as an attachment to the gathered e-mail addresses using the following e-mail format:

TO:


FROM:
The from field may use any of the following format:


Note: %FirstName% may use any of the following:


- and %SecondName% may use any of the following:


- and %random% uses:


- and %domain name% may use any of the following:


Examples:


SUBJECT:
The subject may use any of the following strings:


MESSAGE BODY:
It may use any of the following messages:

ATTACHMENT:
The attachment is a copy of the worm using the following filename format:


%filename% may use any of the following strings:


%ext1% may use any of the following extension names:


%ext2% may use any of the following extension names:


%random%


Example:


The filename is designed to disguise the executable nature of the attachment from the recipient. This worm also uses a text file icon in its attempt to fool recipients into thinking that this file is just a normal text or log file. This is especially true when the - Hide extensions for known file types - option in Windows is enabled. Below is an example.

Readme.txt.pif will be displayed as:




The worm also tries to stop services belonging to different firewalls and to terminate the following processes:



Moreover, Warezov.W also attempts to connect to the following site to download another malware file:

This file download is already detected as Email-Worm.Win32.Warezov.t. This mechanism is used to update the worm from Internet.


The worm uses rootkit features to hide its process in memory. However, our F-Secure BlackLight and F-Secure products that have our Blacklight engine, do detect the hidden process in memory.


Additionally, the worm contacts the yuhadefunjinsa.com website to notify the worm's author. The notification is done with the POST request and it may include some additional data like the worm's version, type and so on.