Terrorists and, other Internet based criminals, are becoming more aware that they are being pursued and observed on the web. Thus, to survive, they are becoming more sophisticated in their use of the web. This has forced investigators and intelligence agencies to stay competitive in order to keep up. For example, a common way for the bad guys to meet is via IRC (Internet Relay Chat), with password protected chat rooms set up in out of the way places so that meetings can be held and information exchanged. Investigators often get access to these locations, but are increasingly finding that the bad guys quickly discovering the true identity of the intruders, and shutting the chat room down. It seems the terrorists have learned to use standard web analysis tools to their advantage. For example, IP addresses (the "telephone number" like ID every Internet user is assigned while online) provide information on the general geographic location of the user. Terrorists will install a program that screens the IP addresses of chat room users, and shut down if they see an IP address from say, North America. To defeat this, agents have to fake their IP address, to make it look like their coming from Yemen, not Virginia. Another terrorist trick is to use only certain operating systems, screen resolution and browsers. All this information can be detected, and if a user does not show the right profile, you have an interloper and its time to shut down the site.
The Internet has been an excellent source of quality information on terrorist activities. Many terrorists, and their supporters, have been sloppy in their use of the web. Better prepared intelligence agents have been able to eavesdrop on a lot of the terrorist Internet activity. This has led to many arrests, and many aborted terrorist attacks. Another benefit is the fear it puts into terrorist Internet users. In many cases, terrorists have stopped using the Internet altogether, fearing whatever "magic" the evil CIA or NSA possesses on the web will inevitably lead to discovery. There is so much turnover among the Islamic terrorists, and so little control over training or communications, that there are always segments of the terrorist population who are online, and vulnerable.