Summary

Update 2003-04-23 09:20 GMT

This worm has been mistakenly referred to as W32.Sars worm because of the SARS theme it uses to bully the recipients of infected messages to open the attachments.

At the time of this update the Coronex worm has not been reported to be in the wild.

Details on the Coronex worm

Coronex is a worm virus spreading via the Internet as an attachment to infected emails. The worm also copies itself to the "C:\My Downloads" directory that may cause other ways of spreading.

The worm itself is a Windows PE EXE file about 12KB in length and is written in Assembler.

The worm activates (from an infected email message) only when a user clicks on the attached file. If this happens the worm starts its installation and spreading routines.

Installing

While installing the worm copies itself to the Windows directory under the name "corona.exe" registers this file in the system registry auto-run key:

 HKLM\Software\Microsoft\Windows\CurrentVersion\Run
  PC-Config32 = %WinDir%\corona.exe

The installation procedure contains bugs, therefore the worm often is not able to install itself into the system, however, despite this the worm is still able to activate its spreading routines.

Spreading: E-Mail

To send infected messages the worm uses a direct connection to the "ns.execulink.com" SMTP server. To get victim email addresses the worm scans the WAB database (Windows Address Book).

The worm activates its spreading routine once per hour (minute:seconds = 1:1).

Infected messages have different "From", "Subject", and "Message body" fields and "Attachment" file names:

 'sars@hotmail.com'
  SARS
  Severe Acute Respiratory Syndrome
  sars.exe

 'sars2@hotmail.com'
  I need your help
  Severe Acute Respiratory Syndrome
  corona.exe

 'corona@hotmail.com'
  Virus Alert!
  SARS Virus
  virus.exe

 'virus@yahoo.com'
  Corona Virus
  honk kong
  hongkong.exe

 'deaths@china.com'
  bye
  deaths virus
  deaths.exe

 'virus@china.com'
  SARS
  SEE Ya
  sars2.exe

 'virus2@china.com'
  SARS Virus
  SARS Corona Virus
  cv.exe

Spreading: MyDownloads

The Coronex worm copies itself to "C:\My Downloads" using the following names:

 'Cossacks Full Version.exe'
 'Battlefield 1942 (full).exe'
 'Warcraft III Full.exe'
 'Jedi Knight II.exe'
 'Quake 3 Full Version.exe'
 'Starcraft full.exe'
 'Doom 3.exe'
 'Tribes 2 (full).exe'
 'Rainbow 6 Full.exe'
 'Oni full.exe'
 'White and Black.exe'
 'Return to Castle Wolfenstien (Full).exe'
 'Command & Conquer: Generals.exe'
 'Black Hawk Down (full).exe'
 'The Sims: Unleashed.exe'
 'Age Of Mythology.exe'
 'Dark Age of Camelot.exe'
 'Ultima Online.exe'
 'The Lord of the Rings.exe'
 'Medel Of Honor: Allied Assault.exe'
 'Grand Theft Auto 3 (full).exe'
 'Unreal 2: The Awakening (full).exe'
 'Unreal.exe'
 'Master Of Orion 3.exe'

After copying itself the worm increases its copy file length to several megabytes.

If there is no "C:\My Downloads" directory, the Coronex worm copies itself to current directory.

Detection in F-Secure Anti-Virus was published on April 22nd, 2003 in update:

[FSAV_Database_Version]

Version=2003-04-22_02

[Analysis: Kaspersky Labs; April 22nd, 2003]