I started a classifieds site with an EMD 1.5-2 years ago. I used OSclass and did a little SEO to the site. I had problems with spam initially using a free script, so I implemented a few security measures. The site didn't move in SERPs much and wasn't a main project so I didn't worry. I actually moved some things around with the site and the security and ended up getting spam classified posts on the site again. I didn't pay too much attention to it but one day took a look and noticed a considerable amount of traffic. The site ended up ranking #4 for "[city] classifieds" and the only thing I can think of that changed was not deleting all the spam posts. The posts are pure contextual and definitely spun, but for awkward keywords/longtail and a few are for prescription medication. The site is still ranked #4 and there are no messages in GWT or any spam indications at all when using OSE/SemRush ect... I am looking to switch CMS and wondering if I should install a new script and just throw away the old content? It doesn't get many spam posts per month anymore, but it only gets 2-3 new ads per day and ads are deleted on auto every 30 days expiration. On a side note can anyone recommend a good classifieds script SEO friendly in 2015?