Low Orbit Ion Cannon (LOIC) is an open-source network stress testing and denial-of-service attack application written in C#.

LOIC was initially developed by Praetox Technologies, however it was later released into the public domain[2] and is currently available on several open-source platforms.

[13][14] In retaliation for the shutdown of the file sharing service Megaupload and the arrest of four workers, members of Anonymous launched a DDoS attack upon the websites of Universal Music Group (the company responsible for the lawsuit against Megaupload), the United States Department of Justice, the United States Copyright Office, the Federal Bureau of Investigation, the MPAA, Warner Music Group and the RIAA, as well as the HADOPI, all on the afternoon of January 19, 2012, through LOIC.

[16] The LOIC application is named after the ion cannon, a fictional weapon from many sci-fi works, video games,[17] and in particular after its namesake from the Command & Conquer series.

The song "Low Orbit Ion Cannon" on Emperor X's 2017 album Oversleepers International directly references the software.