Antispam approaches against information warfare

The term "spam" refers to unsolicited bulk e-mail that people do not want to receive. Today it is gradually becoming a serious problem that results in significant cost both to e-mail receivers and to ISPs (Internet Service Providers). More and more people have become concerned about the issue and are making efforts to develop various anti-spam approaches, some of which are in-process proposals, while others are currently in use. In this chapter, key anti-spam approaches that include filtering, remailers, e-postage, hashcash, and sender authentication, are analyzed and discussed how these antispam approaches can be used against information warfare and cyber terrorism. Furthermore, we analyze vulnerabilities in each approach and recommend possible countermeasures. Technical details and comparisons of each antispam approach are not discussed in this chapter because of space limitations.