Northrop Grumman Technical Services, 13 Mar 08: Changes in Espionage by Americans: 1947-2007
This report documents changes and trends in American espionage since 1990. Its subjects are American citizens. Unlike two earlier reports in this series, individuals are compared across three groups based on when they began espionage activities. The three groups are defined as between 1947 and 1979, 1980 and 1989, and 1990 and 2007. The subset of cases that began since 2000 is given additional study. Findings include: since 1990 offenders are more likely to be naturalized citizens, and to have foreign attachments, connections, and ties.

Their espionage is more likely to be motivated by divided loyalties. Twice as many American espionage offenders since 1990 have been civilians than members of the military, fewer held Top Secret while more held Secret clearances, and 37% had no security clearance giving them access to classified information. Two thirds of American spies since 1990 have volunteered. Since 1990, spying has not paid well: 80% of spies received no payment for espionage, and since 2000 it appears no one was paid. Six of the 11 most recent cases have involved terrorists, either as recipients of information, by persons working with accused terrorists at Guantanamo Bay, Cuba, or in protest against treatment of detainees there. Many recent spies relied on computers, electronic information retrieval and storage, and the Internet. The current espionage statutes have to stretch to cover recent cases that reflect the context of global terrorism.....
Complete 113 page report at the link.