How to store arbitrary data in the bitcoin blockchain and how can I differentiate between a transaction an those data? According to this post, I can store arbitrary data in the blockchain (as the news about "child pornography in the blockchain" tell).
Now I want to store "Hello World" in the blockchain.

Is there a newer website/service that supports me putting data into the blockchain?
And what's the difference between a transaction in the blockchain and such a "message"?
Is the structure different? Why could those researchers even find out that it's inappropriate content instead of a default transaction?
Have a look to these data sources:


https://bitcointalk.org/index.php?topic=1023190
https://github.com/petertodd/python-bitcoinlib/blob/master/examples/publish-text.py


And of course the "modern" (and cheapest) way is storing arbitrary data in segwit part of transactions. I do not know is there ready tool for it, but it is not very difficult to write it.


  Is there a newer website/service that supports me putting data into the blockchain? 


https://cryptograffiti.info/ (based on bitcoin cash blockchain)