Someone might attack on your Linux based system. You can drop attacker IP using IPtables. However, you can use route or ip command to null route unwanted traffic. A null route (also called as blackhole route) is a network route or kernel routing table entry that goes nowhere. Matching packets are dropped (ignored) rather than forwarded, acting as a kind of very limited firewall. The act of using null routes is often called blackhole filtering.
You can nullroute (like some time ISP do prevent your network device from sending any data to a remote system) stopping various attacks coming from a single IP (read as spammers or hackers) using the following syntax on a Linux based system.