This has been well-known inside baseball. They also use cameras/advanced tech to figure out how a pitcher might be tipping their pitches.
I'm surprised former players are admitting it now. I don't know if MLB can retroactively punish the Astros for this because I'm not sure if electronic sign-stealing was prohibited in 2017? I hope they get punished for this.
Again, just like with human umps and an automated strike zone, there exists a technical solution. Have the pitcher and catcher wear an ear piece and have it called in on an encrypted signal. That should solve the problem.
"It was met with, basically, he didn't want to talk about that. He didn't want me to tell him that. I just basically said, 'Well that's why we want an electronic strike zone.'" -- Ben Zobrist