Documents obtained by The Wall Street Journal open a rare window into a new global market for the off-the-shelf surveillance technology that has arisen in the decade since the terrorist attacks of Sept. 11, 2001.

The techniques described in the trove of 200-plus marketing documents, spanning 36 companies, include hacking tools that enable governments to break into people's computers and cellphones, and "massive intercept" gear that can gather all Internet communications in a country. The papers were obtained from attendees...