Twitter and Facebook took action against accounts they said are connected to the Chinese government.
New ad format applies for videos that are 15 seconds or less.
Facebook claims the two developers installed malware on a user's phone in order to generate fake clicks on ads.
Social video site known for lip-syncing uploads chooses Omnicom for global media planning and buying outside of China.
Total number of posts with #ad is forecast to break three-million barrier for first time.
Focus on user authenticity will be seen as challenge to rivals.
Twitter also confirmed it will begin putting warning labels on hate speech by elected politicians.
Double FTC investigations cast shadow over better-than-expected Q2 results.
FTC confirms $5bn Facebook fine, criticises the company's 'deceptive' behaviour, and announces it is suing Cambridge Analytica.
Investigation comes ahead of tech companies facing investors this week.