Low Orbit Ion Cannon
Low Orbit Ion Cannon, or better known as LOIC, is a denial-of-service (DoS) attack program written in C#, the retarded cousin of Java. It has spawned several other clones such as High Orbit Ion Cannon, Snake Bite, and others.
Commonly used by script kiddies, LOIC is often used for attacking websites by sending an obnoxious amount of data packets to crash the target server. In recent years, LOIC has become the trademark weapon of Anonymous. However, as time passed companies had begun arming themselves with DDoS protection. Eventually, Anonymous suggested not to DDoS, rendering LOIC useless. In notable events, LOIC was used by multiple pedophiles in protest of the Church of Scientology and when they were enraged of the take down of their CP on Megaupload by the 4chan Party Van.
Using LOIC can show your uber 1337ness in hacking. When in fact, a DDoS attack does not require any hacking. Normally, you may see a newfag doing this in demonstration.