9.3.8. Social Media – Competitors and Officials must comply with provisions of the INDYCAR Social Media Policy at all times.The probation for Castroneves ends June 30th.
Although the specific violation of INDYCAR's policy was not released, it's assumed that the penalty is in reference to a tweet from Castroneves' official Twitter account following the race containing an image of INDYCAR's logo with a 'thumbs down' symbol on top. The tweet was later deleted and Castroneves' sister, Kati, took blame for the incident in three tweets from her personal account:
My mistake everyone, last tweet on @h3lio account regarding @indycar was posted by me using his account by mistake.
It was supposed to be my account not his. The post was already deleted and @h3lio does not agree with my comments
Sorry again for the tech mistake
The INDYCAR Social Media Policy can be read in its entirety HERE.