WP plugin that flags spam posts (rather than comments)?

I have a WordPress site that allows for users to sign up and guest post blogs. The site is getting a ton of traffic and contributions, but with that comes plenty of spam. It’s similar spam each time, just from a different users and IPs who sign up before being suspended after a spam post or two. Captcha doesn’t prevent it all because the spam is being posted manually.

Is there a WP plugin that blocks spam POSTS, rather than spam COMMENTS?

Something that allows for a blacklist of spam keywords that flags those posts and submits as “draft” rather than “published.”

We’re currently moderating each and every post to avoid spam from making the site upon posting, but that’s becoming difficult to keep up with because of the quantity of posts coming in.

Any help would be appreciated.

Thanks!