Hello mods,

We have developed a number of different ways of fighting spam at Reddit over the years. Most of our effort these days goes into our own back-end tools, which catch ~225,000 pieces of content per day. However, we've gotten feedback that one of our older, less-central tools, the subreddit spam filter, is having some issues.

We want to update you about an ongoing issue a handful of subreddits are experiencing with the subreddit spam filter suddenly becoming overly aggressive. While only a few subreddits have reported experiencing this issue, if both of the below are true then your subreddit is probably one of the unlucky few:

• You had your subreddit spam filter set to "high" for links and/or self posts. (the subreddit spam filter only acts on posts, not on comments)
• Your subreddit noticed that starting around December 4th, there was a big increase in the portion of new posts being filtered to your modqueue.

In the rare case where your subreddit is affected, as an interim solution, we are recommending that you set your spam filter strength to the "low" setting.

Our engineers are still investigating, we have not yet identified the root cause of the problem. With an upcoming code freeze over the holidays, we will continue to monitor the filter's behavior, and the Community Team is still around to assist any affected communities.

It’s important to note that none of our site-wide spam filters are being impacted. In most subreddits the majority of spam is caught by our site-wide filters or automod, the subreddit spam-level spam filter accounts for less than 5% of removals. There isn't any indication when content is filtered by site-wide filters versus the subreddit-level spam filter, which we understand drives a lot of confusion over how spam filtering works across the site.

To provide a recap, here's a summary of the various layers of anti-spam (shamelessly lifted from this post).

• A (now almost as ancient) Bayesian trainable spam filter <- i.e. the thing that is misbehaving
• A fleet of wise, seasoned mods to help with the detection (thanks everyone!)
• Automoderator, to help automate moderator work
• Several (cough hundred cough) iterations of a rules-engines on our backend
• Other more explicit types of account banning, where the allegedly nefarious user is generally given a second chance.

As you can see we have a number of different tools for spam fighting, and only one of which is misbehaving for a few subreddits. We know spam is everyone's favorite topic, so we'll be back to update you in the new year what our longer term plans are for moving forward with this tool.

Edit: Bolded the recommended temporary solution