An intruder may also be able to consume all the available bandwidth on a network by generating a large number of packets directed to the network. Typically, these packets are Internet Control Message Protocol (ICMP) echo packets, but in principle they may be anything. Further, the intruder need not be operating from a single computer; he or she may be able to coordinate or co-opt several computers on different networks to achieve the same effect. This is known as a distributed denial-of-service attack (DDoS).