Summary

This is the worm virus spreading via the Internet being attached to infected emails. The worm itself is Windows PE EXE file about 6Kb of length (compressed by UPX, decompressed size - about 15Kb), written in Visual Basic.

Additional Details

The worm activates from infected email only in case a user clicks on attached file. Note that the real attached .EXE file name is hidden by fake .JPG name (the "extra functionality" of MS Outlook is used for that). As a result the infected .EXE file is displayed as .JPG image file (picture), but on opening this attach it is executed as true EXE file. Starting from MS Outlook 97 SP2 such kind of attached files are blocked (in default mode).

The worm then installs itself to the system, runs spreading routine and payload.

Installation

While installing the worm copies itself to Windows directory with the "csrss.EXE" name and registers that file in system registry auto-run key:

HKLM\Software\Microsoft\Windows\CurrentVersion\Run SystemSARS32 = %WindowsDir%\csrss.EXE
Spreading

To send infected messages the worm uses MS Outlook and sends messages to all addresses found in Outlook address book.

The infected messages have:

Subject: Alert! SARS Is being Spread! Body: Hi!, This is a beta test SARS. Please check an attachment! Attach: sars_image.jpg
The beginning of message body text may be covered by "JPG attach" icon.

Payload

On 1st, 4th, 8th, 12th, 16th, 20th, 24th and 28th of each month the worm deletes all *.DLL, *.NLS, *.OCX files in current directory (in most cases - Windows directory).

F-Secure Anti-Virus detects Melare worm with generic detection and heuristic.

[Kaspersky Lab, 19th of May 2003]