Security firms have cracked down on various forms of malicious software as of late due to the recently elevated amount of threats. Upon doing so, many of the firms have run into seemingly indestructible botnets. These enormous networks of infected systems are numerous, and while many have been dismantled, one of the largest may just be too tough to crack. TDL-4, the fourth version of the malicious TDL software, has an infected network of nearly four and a half million machines. As well, the infected systems communicate through an encryption code created by the makers of TDL-4. The encryption is robust enough to have thwarted all efforts to break it. Without a way to break through, security companies have no way of breaking apart the network, which, at 4.5 million strong could cause serious problems in a short amount of time. Also, as commands can be issued to the network from any of the infected systems, completely decentralizes the network and makes the botnet seemingly impregnable.