TDL-4 is a highly advanced, fourth generation botnet found worldwide (over a quarter of infected machines are in the US) and the name of the rootkit that runs the botnet (also known as Alureon) . Over 4.5 million machines were infected with it in the first three months of 2011, and the botnet continues to grow as no effective measures have been found to prevent it. It infects the master boot record of the target machine, making it harder to detect and remove. Major advancements include encrypting communications, decentralized controls using the Kad network, as well as deleting other malware.