One of the company websites I managed was gravely impacted by bots attack recently. The first indicator was some noticeable changes to the websites standard/original formatting. This creates unsightly pages, poor font placements and bad colour combinations.
Another adverse impact of the bots after gaining access was to target files, preventing seamless updates. It was difficult to detect because the site seems to continue working. Some pages looked like they’re not affected but only because it was showing static page from the cache.