A security update to MacOSX is now released. Among other things it updates the DNS software Bind according to this notice you can see below. An update that is really important to install given that we just started to see effective attacks using this attack vector:
BIND CVE-ID: CVE-2008-1447 Available for: Mac OS X v10.4.11, Mac OS X Server v10.4.11, Mac OS X v10.5.4, Mac OS X Server v10.5.4 Impact: BIND is susceptible to DNS cache poisoning and may return forged information Description: The Berkeley Internet Name Domain (BIND) server is distributed with Mac OS X, and is not enabled by default. When enabled, the BIND server provides translation between host names and IP addresses. A weakness in the DNS protocol may allow remote attackers to perform DNS cache poisoning attacks. As a result, systems that rely on the BIND server for DNS may receive forged information. This update addresses the issue by implementing source port randomization to improve resilience against cache poisoning attacks. For Mac OS X v10.4.11 systems, BIND is updated to version 9.3.5-P1. For Mac OS X v10.5.4 systems, BIND is updated to version 9.4.2-P1. Credit to Dan Kaminsky of IOActive for reporting this issue.