washingtonpost.com: 'SP2' a Must For XP Users "Service Pack 2, "SP2" for short, is Microsoft's most important release since XP itself. It aims to stop viruses, worms, browser hijackings and worse by including security features that people had to add and adjust on their own. (Users of Windows 2000, Millennium Edition, 98 and 95 will still need to do that, since Microsoft has no plans for a comparable update of those systems.)
The most important part of SP2 is an new firewall program to stop break-ins by network worms such as Blaster. Unlike XP's earlier firewall, this one is turned on automatically and protects every connection on a computer -- even if you already have another firewall active. It also watches what your programs do; if one wants to open its own channel of communication with the Internet, you'll need to approve this action.
As part of SP2, the Internet Explorer Web browser now -- finally! -- blocks unsolicited pop-ups. This overdue step eliminates many intrusive ads (yes, The Post's Web site runs its share) but also stops hostile Web sites from tricking users into downloading unwanted programs by barraging them with pop-ups.
To police browser-hijacking attempts, IE now restricts the ability of Web sites to push "ActiveX" programs on visitors; the default choice is to decline an ActiveX program, and you can reject all future installations from a Web site with two clicks. ActiveX should be retired -- this inherently insecure Microsoft technology grants a Web site unrestricted access to your computer -- but these changes should at least make a hijacker's job tougher."