Summary

Updater is a mass mailing worm that is a Windows PE executable. Its size is about 12 KB and it is written in Visual Basic (VB6). It packed by the program UPX. After unpacking its size is 45 KB.

The worm activates from infected email only in case a user clicks on attached file. The worm then installs itself to the system, runs spreading routine and payload.

Additional Details

The infected messages have different texts and attached file names, they are randomly selected by worm while spreading from following variants:

 Subjects are:

  Part1 + Part2 + Part3 + Part4

  Part1 = "Have you ", "You Should ", "Just ", "Why Not you ", "How to ", "Re: ",
          "Fwd : ", " "
  Part2 = "Check ", "Check out ", "Watch out ", "Open ", "Look at "
  Part3 = "this ", "my ", "For this ", "The "
  Part4 = "Picture", "Program", "Patch", "Nude pic", "Report", "Documment",
          "Quotation", "Transaction", "Bank Account", "WTC Tragedy", "Osama Vs Bush"
          "Account", "Private Pic"

Examples:

  You Should Look at this Osama Vs Bush
  Fwd : Check my Patch

Atach filenames are:

  "Setup.EXE", "install.exe", "Readme.exe", "Files.exe", "Picture.exe"
  "Quotation.Doc.exe", "Letter.Doc.exe", "Picture.jpg.exe"

Body:

 Hi:
 This is the file you ask for, Please save it to disk and open this file,
 it's very important.

When the worm is executed, it copies itself to the C:\WINDOWS\ directory with the UPDATE.EXE name and registers that file in system registry auto-run key:

 HKLM\Software\Microsoft\Windows\CurrentVersion\Run
    Update = C:\WINDOWS\Update.exe

The worm then displays a fake error message:

 Cannot Open files : It does not appear to be a valid archive
 if you Downloaded this file , try downloading the file again.
  [ OK ]

Next the worm creates the file C:\WINDOWS\STARTM~1\PROGRAMS\STARTUP\Update.vbs. This script file starts automatically after rebooting system under Windows 9x/ME. It looks for files on all drives with expansions: EXE, DOC, TXT. It creates script copies with the same names + expantion: ".vbs" For example:

  MPLAYER.EXE.vbs
  NOTEPAD.EXE.vbs

This script file contains the strings:

 I-WORM.IMELDA.B

The worm changes a volume label on disk C: the the IMELDA.

The worm also copies itself to the C:\WINDOWS\ directory with one of this names:

 "Setup.EXE", "install.exe", "Readme.exe", "Files.exe",
 "Picture.exe" "Quotation.Doc.exe", "Letter.Doc.exe", "Picture.jpg.exe"

[Analysis: Kaspersky Labs, December 7th, 2001.]