LOIC performs a DoS attack on a target site by flooding the server with TCP, UDP, or HTTP packets with the intention of disrupting the service of a particular host. People have used LOIC to join voluntary botnets. The software inspired the creation of an independent JavaScript version called JS LOIC, as well as LOIC-derived web version called Low Orbit Web Cannon. These enable a DoS from a web browser.
Countermeasures
Security experts quoted by the BBC indicated that well-written firewall rules can filter out most traffic from DDoS attacks by LOIC, thus preventing the attacks from being fully effective. In at least one instance, filtering out all UDP and ICMP traffic blocked a LOIC attack. Because internet service providers provide less bandwidth to each of their customers in order to provide guaranteed service levels for all of their customers at once, firewall rules of this sort are more likely to be effective when implemented at a point upstream of an application server's internet uplink. In other words, it is easy to cause an ISP to drop traffic destined for a customer by sending a greater amount of traffic than is allowed on that customer's link, and any filtration that occurs on the customer side after the traffic traverses that link will not stop the service provider from dropping excess traffic destined for that customer. LOIC attacks are easily identified in system logs, and the attack can be tracked down to the IP addresses used.
LOIC was used by Anonymous during Project Chanology to attack websites from the Church of Scientology, once more to attack the Recording Industry Association of America's website in October 2010, and it was again used by Anonymous during their Operation Payback in December 2010 to attack the websites of companies and organizations that opposed WikiLeaks.
The LOIC application is named after the ion cannon, a fictional weapon from many sci-fi works, video games, and in particular after its namesake from the Command & Conquer series. The artwork used in the application was a concept art for .
Legality
While downloading and using the LOIC on one's own personal servers as a means of stress-testing is perfectly legal at least in the United States, using the program to perform a DDoS attack on other parties could be considered a felony under the Computer Fraud and Abuse Act of 1986. This charge could result in up to 20 years of imprisonment, a fine or both.