Apple has released their new Security Update 2008-005. This update should be installed as soon as possible as this security update patches some vulnerabilities (especially a DNS/BIND server vulnerability) where an attacker could cause a Mac OS X DNS server to direct users to forged websites.
This means instead of accessing a website you want to go to, an attacker could take advantage of this DNS/BIND vulnerability and direct you to a fake website where there is a chance you would enter personal information, thus giving away your information to attackers.
This update is available via Software Update.
