IT administrators who are inclined to dismiss the dust storm that has blown up over Sony BMG Music Entertainment's digital rights management rootkit might want to reconsider. Vulnerabilities in Web and client/server applications <A HREF="http://www.eweek.com/article2/0,1895,1889029,00.asp?kc=ewnws112105dtx1k0000599">are becoming the new battleground</A> in the war against malicious hackers, as holes in network perimeters and Web servers become harder to find and exploit. That's the good news, but shoring up applications against security vulnerabilities will be harder than plugging holes in Web servers or network firewalls, security experts agree.