I'm dealing with a site (not Wordpress, nor any other CMS) that was previously hacked and at that time I had found a php file in the images directory that was being used to generate spam from the site. Now I've watched the 404 errors climb back into the 2000+ range in webmaster tools. People have told me not to worry about this, but a large number of 404 errors preceded the previous issue, and I had to go through the whole resubmission/reconsideration ordeal with Google. At this point, running the site check on Sucuri's website shows this site is blacklisted, but only with them (Sucuri) at this point.
I can't track down any funny looking code or files on the server, and I've changed the FTP login information. I do see viagra and cialis links in the log files, but don't know how to use this information to clean up the site or protect it better. At one point, I was blocking specific URLs within my htaccess, but this doesn't seem to have an effect anymore. The client is hesitant to switch hosts. Any suggestions about how I can use what I am seeing in the logs to disassociate my site from the spammers?