Threat Description



Aliases: Email-Worm.Win32.Warezov.c
Category: Malware
Type: Email-Worm
Platform: W32


This type of worm is embedded in an e-mail attachment, and spreads using the infected computer's e-mailing networks.


Automatic action

Once detected, the F-Secure security product will automatically disinfect the suspect file by either deleting it or renaming it.


Detailed instructions for F-Secure security products are available in the documentation found in the Downloads section of our Home - Global site.

You may also refer to the Knowledge Base on the F-Secure Community site for further assistance.

Technical Details

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

Warezov.C also downloads another trojan from a specified website on the Internet.


When executed, the worm creates a temporary file in the directory where the malware was executed using the following filename:

  • %NumTimes%.tmp

Note: %NumTimes% is the number (value is in hexadecimal) of times the malware was executed on the computer system.

This created temporary file contains random characters inside and is displayed using notepad upon execution of the malware. This is used as a stealth mechanism to fool the users into thinking that this was the file executed instead of the actual worm. Below is a sample of the displayed image:

It also drops the following files:

  • %WinDir%\rsmb.dll - DLL component of the worm, also detected as Email-Worm.Win32.Warezov.C
  • %WinDir%\rsmb.exe - A copy of itself
  • %WinDir%\rsmb.z - Log file
  • %WinDir%\rsmb.dat - Log file0

To ensure its execution every system startup, Warezov.C creates the following autostart registry entry:

  • [HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion\Run] smb = "%WinDir%\rsmb.exe s"

Note: %WinDir% is by default C:\Windows or C:\WINNT


In addition to propagating itself, Warezov.C also attempts to connect to the following site to download another malware file:


This attempted downloaded file is already detected as Trojan.Win32.Agent.wc.


It harvests email addresses from the infected system by scanning through files with the following extension names:

  • asp
  • cfg
  • cgi
  • dbx
  • eml
  • htm
  • htm
  • html
  • jsp
  • mbx
  • mdx
  • mht
  • mmf
  • msg
  • nch
  • ods
  • oft
  • php
  • pl'
  • sht
  • shtm
  • stm
  • tbb
  • txt
  • uin
  • wab
  • wsh
  • xls
  • xml

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

TO: {Gathered email address from the system}

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

  • %FirstName% %SecondName% <%FirstName%.%SecondName%@%domain name%>
  • %FirstName% <%SecondName%_%random%@%domain name%>

Where %FirstName% may use any of the following:

  • adam
  • alice
  • anna
  • betty
  • bob
  • brenda
  • brent
  • brian
  • carol
  • claudia
  • craig
  • cyber
  • dan
  • dave
  • david
  • debby
  • den
  • Donna
  • frank
  • george
  • gerhard
  • helen
  • helen
  • james
  • jane
  • jayson
  • jerry
  • jim
  • joe
  • john
  • karen
  • linda
  • lisa
  • mancy
  • maria
  • ruth
  • sandra
  • sandra
  • sharon
  • Susan

%SecondName% may use any of the following:

  • adams
  • allen
  • anderson
  • baker
  • carter
  • clark
  • garcia
  • gonzalez
  • green
  • hall
  • harris
  • hernandez
  • hill
  • jackson
  • jeremy
  • joe
  • kenneth
  • king
  • lee
  • lewis
  • lopez
  • martin
  • martinez
  • miller
  • molly
  • moore
  • nelson
  • robinson
  • robyn
  • rodriguez
  • scott
  • shaan
  • taylor
  • thomas
  • thompson
  • walker
  • white
  • wilson
  • wright
  • young

%random% uses:

  • Random 4-digit characters

And %domain name% may use any of the following:



  • james nelson (
  • sandra (

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

  • Good Day
  • Error
  • Hello
  • Mail Delivery System
  • Mail Transaction Failed
  • Picture
  • Server Report
  • Status
  • Test

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

  • Mail transaction failed. Partial message is available.
  • The message cannot be represented in 7-bit ASCII encoding and has been sent as a binary attachment.
  • The message contains Unicode characters and has been sent as a binary attachment.

Below is an sample screenshot of the e-mail message the worm is delivered in:

ATTACHMENT:The attachment is a copy of the worm. The filename is designed to disguise the executable nature of the attachment from the recipient. It is created using the following filename format:

  • %filename%.%ext1%.%ext2%

Where %filename% may use any of the following strings:

  • body
  • data
  • doc
  • docs
  • document
  • file
  • message
  • readme
  • test
  • text

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

  • dat
  • elm
  • log
  • msg
  • txt

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

  • bat
  • cmd
  • exe
  • pif
  • scr


  • readme.txt.scr

This worm also uses a text file icon in its attempt to fool recipients that this file is just a normal text or log file. This is especially true when the Hide File Extensions option in Windows is enabled. Below is an example:


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