You can run an advanced traffic trade script on the site. The script will tell you from which the urls the traffic is coming from and how much. The script has special features that can tell you where the fake traffic and hit bot traffic coming from.
Usually, the way to tell whether the traffic is abnormal or not is to look at the productivity.
1 person enters site and makes 2 clicks
vs
1 person enters site and makes 100 clicks
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