Around 1 year ago we got hit badly on our [blogging platform][0] by people/groups submitting fake customer support description of other big companies, either being Microsoft, Facebook, Comcast etc.
Rolled out a machine learning model and trained it on the database. 99% of them vanished.

Next day, the machine didn’t work and success rate was around 5%.

Found out, they have learned the trick and now using symbols from different languages to make it look like English.

Trained again, success rate went up again.

Next hour, success rate fallen.

This time, they mixed their content with other valid content of our own blogging platform. They would use content from our own blog or other people posts and mix it to fool the machine learning.

Trained it again and was success.