If you run either BlackICE(tm) Defender 2.9 or BlackICE(tm) Defender for Server 2.9 on Microsoft Windows 2000/XP, you'll want to download the product updates right away.
The glitch allows an attacker to intentionally crash or take control of computers running this software by sending a series of packets known as a ping flood. Product updates are available at http://www.iss.net/support/consumer/BI_downloads.php