[jmward01]

I'm not a lawyer but it would be odd if a government agency couldn't communicate a possible threat to a tech company. It is in a company like LinkedIn's best interest to set up a phone number/channels for a centralized agency to communicate potentially malicious accounts and other emerging threats. I suspect that actually already exists for big companies. I doubt they are required to -do- anything without laws but this seems like a win that is easy for all sides. The problem is likely mostly on the US (and other govt) side of things. No clearly defined agency with a clear mandate, resources and leadership to take on this task.

[evilduck]

You're describing the FBI or your state level equivalent. And they actually do exactly what you are describing, but in measured efforts. I've even had them come by my place of employment before. They clearly lack the resources to work at this scale though.

The problem with a phone number you suggest is that it will get spammed and abused with fraudulent imposters too (the complete and utter destruction of trust in phone calls and text messages should also be corrected by the government, but that's a different topic).

https://www.fbi.gov/investigate/cyber