Search engines may issue a manual or algorithmic penalty to any websites they deem to be spam-like in nature. These penalties make it difficult for the site to rank well on the SERPs. Algorithmic penalties are often lifted once the site makes the necessary corrections. Manual penalties may require the webmaster to submit a request to the search engine to be re-evaluated.
Websites are not notified if they have been penalized. It is best to monitor website ranking for this reason. If a site is penalized, run a penalty and recovery audit to determine how to solve the issues.