Communities on Google+ will now be able to take a stronger stand against spam thanks to a new content controls setting. Rolling out to existing Communities now, the new setting will allow for more aggressive content filtering to keep spam to a minimum.

From Google Product Manager Frank Rodriguez:

Now we can be more aggressive in identifying inappropriate posts in a Community. When this setting is on, Google+'s content filter is more likely to flag posts that are questionable, so fewer of them will show up in your Community. Check your moderator queue to see these blocked posts.

Google+ helps Communities fight spam with new content controls setting

As Rodriguez notes, the setting will be on by default for newly created Communities. However, existing communities will see the setting enabled via a gradual rollout.