I do not, ActivityPub uses HTTP signatures to make sure messages and requests from other servers are legit,

Essentially, it adds a "signature" header which contains a link to a users public key, a list of headers in the message and a signed hash of all the headers and the request.

There's a better explaination here: https://docs.joinmastodon.org/spec/security/

A delicated bot to scrape ActivityPub posts is possible, but generic bots shouldn't work. If a delicated bot is made, people can block its keys or server anyway.