This looks like a broadcast sent by someone logged in as root using the
wall utility. You can use this same command to broadcast your own message. Eg:
wall "Hello back"
wall << EOF
If you just want to respond to a single user without broadcasting to everyone on your system you can use
write root << EOF
Obviously the fact that this says from [email protected] infers that someone is logged in as
root. If you know that nobody but you is supposed to be logged in as root then take action because it infers your machine has been compromised.