今天晚上，我的服务器被黑了，屏幕如下图示，后面是我被修改的主页文件，请高手给看看，他怎么进来的，我的漏洞是什么？
index.php
<title>#Hacked By Ramzi Null#</title><link href="http://hacker-newbie.org/favicon.ico" rel="shortcut icon" type="image/x-icon" />
<style type='text/css'>
body,td,th {
font-family: Impact;
font-size: 13px;
color:#00FF00;
}
body {
background-color:#121214;
}
a:link {color: #FFFFFF; text-decoration: none; }
a:active {color: #FFFFFF; text-decoration: none; }
a:visited {color: #FFFFFF; text-decoration: none; }
a:hover {color: #00FF00; text-decoration: none; }
</style>
<script type="text/javascript">
<!--//
function tb9_makeArray(n){
this.length = n;
return this.length;
}
tb9_messages = new tb9_makeArray(4);
tb9_messages[0] = "#Hacked By Ramzi Null";
tb9_messages[1] = "#Tunisia Hackers";
tb9_messages[2] = "..................";
tb9_messages[3] = "|";
tb9_messages[4] = "<========== | ==========>";
tb9_messages[5] = " <===== | =====> ";
tb9_rptType = 'infinite';
tb9_rptNbr = 5;
tb9_speed = 75;
tb9_delay = 2000;
var tb9_counter=1;
var tb9_currMsg=0;
var tb9_timerID = null
var tb9_bannerRunning = false
var tb9_state = ""
tb9_clearState()
function tb9_stopBanner() {
if (tb9_bannerRunning)
clearTimeout(tb9_timerID)
tb9_timerRunning = false
}
function tb9_startBanner() {
tb9_stopBanner()
tb9_showBanner()
}
function tb9_clearState() {
tb9_state = ""
for (var i = 0; i < tb9_messages[tb9_currMsg].length; ++i) {
tb9_state += "0"
}
}
function tb9_showBanner() {
if (tb9_getString()) {
tb9_currMsg++
if (tb9_messages.length <= tb9_currMsg) {
if ((tb9_rptType == 'finite') && (tb9_counter==tb9_rptNbr)){
tb9_stopBanner();
return;
}
tb9_counter++;
tb9_currMsg=0;
}
tb9_clearState()
tb9_timerID = setTimeout("tb9_showBanner()", tb9_delay)
}
else {
var tb9_str = ""
for (var j = 0; j < tb9_state.length; ++j) {
tb9_str += (tb9_state.charAt(j) == "1") ? tb9_messages[tb9_currMsg].charAt(j) : "___"
}
document.title = tb9_str
tb9_timerID = setTimeout("tb9_showBanner()", tb9_speed)
}
}
function tb9_getString() {
var full = true
for (var j = 0; j < tb9_state.length; ++j) {
if (tb9_state.charAt(j) == 0)
full = false
}
if (full) return true
while (1) {
var num = tb9_getRandom(tb9_messages[tb9_currMsg].length)
if (tb9_state.charAt(num) == "0")
break
}
tb9_state = tb9_state.substring(0, num) + "1" + tb9_state.substring(num + 1, tb9_state.length)
return false