Search the files and database of your WordPress install for signs that may indicate that it has fallen victim to malicious hackers.
It is likely that this scanner will find false positives (i.e. files which do not contain malicious code). However, it is best to err
on the side of caution; if you are unsure then ask in the Support Forums,
download a fresh copy of a plugin, search the Internet for similar situations, et cetera. You should be most concerned if the scanner is:
making matches around unknown external links; finding base64 encoded text in modified core files or the
listing extra admin accounts; or finding content in posts which you did not put there.
Understanding the three different result levels:
Follow the guides from the Codex:
Ensure that you change all of your WordPress related passwords (site, FTP, MySQL, etc.). A regular backup routine (either manual or plugin powered) is extremely useful; if you ever find that your site has been hacked you can easily restore your site from a clean backup and fresh set of files and, of course, use a new set of passwords.
Unfortunately for people using WordPress versions for other locales some of the file hashes may be incorrect as some strings have to be hardcoded in their translated form. Here are some file hashes for WordPress in other languagues provided separately by other members of the community:
The hash files should only be declaring an array called $filehashes and the majority of the hashes should still be the same.