As Middle East regimes try to stifle dissent by censoring the Internet, the U.S. faces an uncomfortable reality: American companies provide much of the technology used to block websites.

McAfee Inc., acquired last month by Intel Corp., has provided content-filtering software used by Internet-service providers in Bahrain, Saudi Arabia and Kuwait, according to interviews with buyers and a regional reseller. Blue Coat Systems Inc. of Sunnyvale, Calif., has sold hardware and technology in Bahrain, the United Arab Emirates and Qatar that has been used in conjunction with McAfee’s Web-filtering software and sometimes to block websites on its own, according to interviews with people working at or with ISPs in the region. More>>