Ask HN: How to catch GA hack?

What are the most powerful hard evidence to prove that a website is facing a Google Analytic hack.

I am suspecting that my supplier is hacking the campaign website to reach the UV/ page view KPI. With no other promotion going on, UV is jumping straight from 70~80/day to 2300/today. Traffic breakdown are: 2,000 (direct link); 300 (referral); 1 (organic).

From the direct and referral, 94% and landing to www.homepage.com/?from=app ; instead of www.homepage.com

Visiting time is distributed throughout the day; 75% of visitor are coming from 5 areas, 4 of the area are located in 2 tier cities.

But, what will be the best way to prove it?