Problems
Such webmasters realise that they are working with a banned traffic source. Thus, they try to hide it in every way possible, for example, by using geotargeting, different devices, and more.
Challenges
To filter out such traffic effectively, you need to monitor your branded search results 24/7 from different devices, regions, different times of the day, IP addresses, etc.
Risks
It is almost impossible to do it manually and sifting out such traffic by behavioural factors, you risk cutting off diligent and conscientious webmasters.
