Distributed denial of service attack
A distributed denial of service attack is the use of many computers (typically a botnet) to send an overwhelming quantity of requests to one or more targeted servers in order to overload the victim. These attacking devices attempt to act like legitimate users, so the target server(s) has a difficult time discerning between legitimate requests and fraudulent ones. It will therefore try to respond to all requests. A successful DDoS attack results in the victim being unable to reply to many of the incoming requests, including the legitimate ones, so real users will see timeout errors when trying to access the service. In some cases, an ISP might also temporally disconnect the victim from their network, in order to remain functional for their other clients. DDoS attacks are often carried out against political adversaries (such as opposing governments) to impair their ability to operate, but can also be perpetrated against competitors or rivals for the purpose of redirecting customers or viewers to the attacker's service. DDoS attacks are illegal in many countries; in the US, perpetrating a DDoS attack is punishable by up to 10 years in jail.
DDoS attacks are also sometimes used as an extortion tactic. In this scenario, an attacker begins a persistent DDoS attack on a selected victim's systems, then contacts that victim demanding that they pay a ransom in order to have the DDoS attack stop. This can be quite problomatic for the victim, since such an attack does not require the attacker to find any security vulnerabilities in the victim systems. However, this can be difficult to perpetrate due to the technical requirements, and doing this puts the attacker's bots at risk of being discovered and lost. Oftentimes, other DDoS attack mitigation strategies are successful at stopping such an attack.