On July 8, security researcher Dan Kaminsky announced he planned to reveal details about the DNS vulnerability (DNS cache poisoning) at Black Hat. Since then, many technology vendors have provided patches to help fix the flaw.
Kaminsky has provided a "DNS Checker" self test on his website - see his personal blog at http://www.doxpara.com/
Link to Wall Street Journal article about the security vulnerability - http://blogs.wsj.com/biztech/2008/08/06/disclosing-a-hole-in-the-internet/
Link to InformationWeek article about the security vulnerability - http://www.informationweek.com/news/security/vulnerabilities/showArticle.jhtml?articleID=209903948