In the fallout resulting from knocking McColo Corp. offline, this past week may prove to be a missed opportunity in the prevention of a dramatic reappearance of junk e-mail, as a botnet that once controlled 40 percent of the world’s spam apparently has found a new home. The botnet Srizbi was knocked offline Nov. 11 along with Web-hosting firm McColo, which Internet security experts say hosted machines that controlled the flow of 75 percent of the world’s spam. One security firm, FireEye, thought it had found a way to prevent the botnet from coming back online by registering domain names it thought Srizbi was likely to target. But when that approach became too costly for the firm, they had to abandon their efforts. “This cost us a lot of money. We engaged all the right people. In the end, it comes back to the fact that there wasn’t a process