I will limit this to Hegseth as he is squarely in an area I can speak specifically about. Every DoD civilian employee is required to complete training on a yearly basis as to handling of different types of classified information, from CUI all the way up to PPI. All of those are considered sensitive and would run the gamut from your boss's phone number (PII) up to state secrets. Government phones come with the same texting ability as the phone in your hand. What they are saying is not to use iPhone messenger, use the signal app if you are having any discussions. Sensitive would include sharing the direct contact information of a base commander. Things that are publically available can be considered sensitive when it is being passed from one government worker to another.
Hegsett is a former officer and has likely had an even more in depth briefing than a typical DoD civilian. He absolutely knows that you CANNOT transmit the information he did over Signal or any other off the shelf app out there.
@Aloha Hoosier is 100% accurate in his description of the different methods they have available to have this level of discussion. Giving times, type of aircraft, target data, etc. before an attack increases the risk involved for our service members. This was an absolute shit show of a **** up on Hegseth's part. He has to be the example to the people he leads and every single one of them knows that there was no way in hell he didn't know he was in the wrong sharing that data. It doesn't matter one damn bit what CISA has to say because DoD is very clear on the rules, he would be facing termination, fines, and potentially jail if he wasn't a political appointee. The political operatives in both parties have gotten really loose with INFOSEC and it needs to stop. What Hegseth shared could literally get people killed.
So I won't be as nice. Conservatives, there is no ifs, ands, or buts around this. They ****ed up. They need to issue their mea culpas. They need to stop using these apps to try and skirt FOIA and Presidential Record keeping laws. There isn't a needle to thread here.