command-and-control
how an attacker sends orders to systems it has broken into
After breaking in, an attacker needs a way to send instructions and receive results. That channel is called command-and-control. Modern attackers often hide it inside ordinary services, such as paste sites or file uploads, so it blends with normal traffic. Defenders look for unusual patterns rather than one known address.
Think of it as
A spy leaving notes inside a public library book instead of making phone calls.
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