Tighter physical and border security may encourage terrorists and extremists to try to use other types of weapons to attack the United States. Persistent Internet and computer security vulnerabilities, which have been widely publicized, may gradually encourage terrorists to develop new computer skills, or develop alliances with criminal organizations and consider attempting a cyberattack against the U.S. critical infrastructure. Cybercrime increased dramatically between 2004 and 2005, and several recent terrorist events appear to have been funded partially through online credit card fraud. Reports indicate that terrorists and extremists in the Middle East and South Asia may be increasingly collaborating with cybercriminals for the international movement of money, and for the smuggling of arms and illegal drugs. These links with hackers and cybercriminals may be adding to terrorists' computer skills, and finances obtained through drug trafficking may also provide terrorists with access to highly skilled computer programmers. The July, 2005 subway and bus bombings in England also indicate that extremists and their sympathizers may already be embedded in societies with a large information technology workforce. The United States and international community have taken steps to coordinate laws to prevent cybercrime, but if trends continue computer attacks will become more numerous, faster, and more sophisticated. In addition, a recent report by the Government Accountability Office states that, in the future, U.S. government agencies may not be able to respond effectively to such attacks. This report examines possible terrorists' objectives and computer vulnerabilities that might lead to an attempted cyberattack against the critical infrastructure of the U.S. homeland, and also discusses the emerging computer and other technical skills of terrorists and extremists. Policy issues include exploring ways to improve technology for cybersecurity, or whether U.S. counterterrorism efforts should be linked more closely to international efforts to prevent cybercrime. This report will be updated as events warrant.