Biggest threat to website negative SEO
Forced Crawling
There are examples of desperate website owners trying to block a competitor's website by forcibly crawling it and causing a heavy load on the server. If Googlebot can't access your site multiple times in a row ... you guessed it, you could be disqualified.
How to stay safe:
If you notice that the site has become slow or, what is worse, is not available, it is recommended to contact the hosting company or the webmaster; they must inform the origin of the load. If you know anything about server logs, here are some detailed instructions on how to find villain trackers and block them with robots.txt and .htaccess.
Negative SEO on the page
Negative SEO attacks on the page are much more difficult to implement. This involves breaking into their website and changing things. These are the main SEO threats that a hacker attack can pose.
Unindex your site for various reasons
A small change in robots.txt is a change that can wreak havoc on your entire SEO strategy. Just a ban rule to tell Google to completely ignore your site.
There are several examples of this online, including this story. One client fired an SEO agency they were unhappy with, and their revenge was adding a Prohibition rule: / to the client's robots.txt file.
How to stay safe: Regular ranking checks will help you be the first to know if your site is indexed. With the online ranking checker, you can schedule automatic scans to take place daily or weekly. If your site suddenly falls out of search engine results, you will see a deleted note in the Difference column.
When this happens on a large number of keywords, it usually involves a penalty or de-indexing. If you suspect this, check the tracking statistics in your Google Search Console account and take a look at your robots.txt.
