Many times when you download wordpress themes there is some sort of encrypted coding which looks like malicious code in either footer.php or in other files.Though many times it is given for just copyright and licensing of template but it might be dangerous too as it may attempt to steal your website user info or other stats.
These plugins will make your life easier
1)Html Purifier
HTML cleanup, is standards-compliant HTML filter library written in PHP. HTML cleaner will not only remove all malicious code (better known as XSS) and checked thoroughly safe yet permissive whitelist, it will also ensure that your documents are standards compliant, something only possible with a comprehensive knowledge of W3C specifications . Tired of using BBCode is because the landscape is either inadequate or insecure HTML filters? Do you have a WYSIWYG editor but never been able to use it?
Looking for high quality, standards, open-source components for applications that you build? HTML Purifier is for you! Know your enemy. Hackers have a huge arsenal of XSS vectors in the hidden depths HTML specifications. HTML Purifier is effective because it covers the whole document
the tokens and the removal of non-white elements, such as well-formed ness checking and nesting of tags, and validate all the attributes of their RFCS.
HTML cleaner complex algorithms are complemented by the breadth of knowledge to ensure that rich-formatted documents undergo unstripped.
http://htmlpurifier.org/releases/htmlpurifier-3.3.0.zip
Note : They also have some links in their file (html-purified.php )you can remove it by editing it.Other wise they will be replacing into your page footer.
2)TAC (Theme Authenticity Checker)
TAC stands for authenticity Topic Checker. TAC is currently looking for source files of all installed signs of malicious code issue. If a number is found, TAC displays the path of the file, line number, and a small fragment of the suspect code. Chances are not because there is no logical reason base64 encoding in the subject line.
Static Links are not necessarily bad, but a list of TAC’s and see where your topic is a link to.If something malicious or simply unwanted.
# NEW! Controls Embedded Static Links
# NEW! Direct links to edit files on suspected WordPress Theme Editor
# Improved CSS
# Uses a custom function to get theme file paths
http://downloads.wordpress.org/plugin/tac.1.3.zip
3)WordPress Exploit Scanner
This plugin searches the files on your website, and the posts and comments tables of your database for anything suspicious. It also examines your list of active plugins for unusual filenames.
It does not remove anything. That is left to the user to do.
http://downloads.wordpress.org/plugin/exploit-scanner.0.4.zip
