Chir.B

It overwrites files with certain extensions and exploits two vulnerabilities in Internet Explorer.

Windows 2003/XP/2000/NT/ME/98/95

Chir.B is a worm that reaches computers in an e-mail attachment called PP.EXE. The subject of this message consists of the sender's name followed by the text is coming!.

It is easy to get infected with this worm, as it activates automatically when the message is opened or just viewed through Outlook's Preview Pane.

In order to do so, it exploits two vulnerabilities: Exploit/iFrame and Exploit/MIME. These vulnerabilities allow files attached to e-mail messages to be run automatically.

This is a dangerous worm, as it infects files with the following extensions: EXE, SCR, HTM and HTML. Besides, Chir.B has destructive effects, as on the first day of each month it overwrites the first 4,660 bytes of files with the following extensions: ADC, R.DB, DOC and XLS.

A clear indication that you have received Chir.B is a message with the following characteristics:

• Sender: one of the following:
  %sender's name%@yahoo.com
  Imissyou@btamail.net.cn
• Subject:
  %sender's name% is coming!
• Message: it does not contain any text.
• Attachments:
  PP.EXE