The FBI has issued an alert warning of possible cyberterrorism from al Qaeda or related groups. But the FBI also cautioned American hackers to refrain from attacks, or counterattacks, as there is risk that some of these actions can cause collateral damage (causing unintentional damage to allied nations.) While most cyberwar between Islamic radicals and the rest of the world has so far largely been of the web page defacement and mail bombing (sending thousands of messages to one mail box) variety, the potential is there for more dangerous attacks. The FBI fears that, if an Islamic group did pull off a serious Internet attack (shutting down a major American site for hours or days, or slowing down traffic to a noticeable degree), some American hackers might respond by trying to shut down Internet access in one or more Islamic nations. This is easier to do in the smaller Internet markets, because there is less, and simpler, Internet infrastructure to go after. Such an attack could knock, say, Pakistan off the Internet for several days.