That was what protected the Wall. Killer-countermeasures intended to wreck an intruder’s equipment and quite possibly take his life. The presence of such deadly software meant that Renraku so valued whatever was behind the Wall that the corporate masters had no compunction about sending deadly electrical impulses through the lines to fry the brain of anyone who illegally accessed their system. Killer ice was illegal, but its use was never reported to the authorities because it was always directed against criminal intrusion. The corporate world of the twenty-first century relied on the old adage that dead men tell no tales. But now Sam had seen the killer ice in action, and lived to tell about it.