I am sure they had pilot communications data mined from satellites picking off every electromagnetic transmission in the entire nation of Syria. We probably have conversations between Bashar al-Assad and his mistress. Asma would probably kill him if she knew what he was up to.
I hate CNN but they are reporting just that - pilot comms.
http://www.cnn.com/2017/04/12/politics/us-intelligence-syrian-chemical-weapons/index.html