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A botnet is a number of Internet-connected devices, each of which is running one or more bots. Botnets can be used to perform Distributed Denial-of-Service attacks, steal data, send spam, and allows the attacker to access the device and its connection.Botnets are created by infecting multiple systems with malware (malicious software) and thus rendering them to be slave systems to the botnet operator. This malware can be introduced to a computer system in various forms, for example: A trojan within an email attachment.