WordPress comment spam

In the past few days I’ve been inundated with comment spam. I suppose the spammers respond when an inactive blogger starts posting again. So I changed my WordPress settings to close comments automatically on postings older than 28 days (most of the spams were comments on old postings, not the recent ones). Sadly that seems to have stopped it displaying the old, approved comments as well! They are still there in the database but they don’t display unless I re-open the posts for comments. I guess this is going to require some hacking of my theme, and I haven’t time, so it will languish on the to-do list for now.