Textspianoge 

The act of reading the texts of someone you know without their knowledge.

Word play: (text espionage)

Jason committed textspianoge on his ex girlfriend due to jealousy.

Textspianoge by acyis September 10, 2019

Textspionage 

when you obtain information that is considered secret using text messages

My coworker uses her textspionage skills to gather the latest news and gossip at work.

Textspionage by BlaqueIceX March 11, 2012