While WordPress is typically a secure and stable platform, it can fall victim to hackers when not maintained, or when poorly developed or outdated plugins are used. One of the more common methods for hackers to hide the malicious PHP code inserted in to WordPress is to base64 encode the hacked code, and then use base64 decoding and eval() to execute the code at runtime.
Original post by Internet-and-Businesses-Online:Security Articles from EzineArticles.com