How do I tell if a wordpress theme has a virus?

I download wordpress themes from here quite often, but I have read in other forums that sometimes they will have viruses or malicious code inserted into them. How do I check if a wordpress theme that I have downloaded has some type of virus or malicious code? Does virustotal.com find viruses in wordpress themes? Any suggestions?
Thanks.
Answer #1
http://wordpress.org/support/topic/how-to-scan-a-themesite-for-any-malicious-code-virus-bad-script-exploit
http://www.wpstuffs.com/detect-malicious-code-wordpress-themes-plugins/
GOOGLE
Answer #2
That is a good start, but it will not detect all exploits/back doors. You will never be 100% sure unless you review the code.