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Conficker was malware intended to create a botnet. Until recently, botnet controllers would instruct malware to connect with a few dozen fixed domains in order to control the machines. As security experts improved and blocked these domains, the malware authors expanded their sophistication, targeting many more domains. With early versions of Conficker, the infected computer would reach out to 250 pseudo-randomly generated domains per day from eight Top Level Domains (TLDs) to attempt to update with new code or new instructions.