Our client came to us from PeoplePerHour and had seen a huge drop in traffic. This aged website was historically a well-performing authority niche site and the client had not made any major changes that would warrant such a major drop.
Through performing various reports and analysis, I found a huge number of toxic links pointing to the client’s domain. These were, I’m afraid, of the worst kind and as such, Google picked these up, resulting in a loss of rankings and reputation. This wasn’t done by anyone working with the client and could have been an attack from a rival competitor.
I quickly disavowed the URLs with Google and the client’s traffic returned. This can happen to anyone, which is why we’d recommend monitoring your website to be alerted to such changes. Make sure you have Google Search Console (previously Google Webmaster Tools) and Google Analytics connected to your website for this reason.