Why, they wondered, had Boyle -- who appeared on national television last Sept. 13 to campaign against U.S. involvement in Afghanistan -- written "when I see in the newspapers that civilians in Afghanistan or the West Bank were killed by American or Israeli troops, I don't really care"?

The answer was simple. The message that supposedly came from Boyle was a forgery -- one of thousands sent out in the names and from e-mail addresses of prominent advocates for the Palestinians -- designed to sow dissension, create confusion and waste time in the activist community.

"Primarily, it's been a frustrating nuisance. But there have been a lot of angry misunderstandings, creating a lot of distraction," said Nigel Parry, co-founder of the Electronic Intifada website. "Some people are closing accounts, others are getting off (activist e-mail) lists entirely."

Palestinian and Israeli hackers have been going after each other since the latest round of Middle East violence erupted in September 2000. But this tactic, e-mail identify theft -- known as a "Joe job" by spam experts -- is a new one, possibly the most disruptive yet.

Boyle, a professor of international law at the University of Illinois, spent nearly four days sifting through the messages, writing personal apologies to the offended and manually deleting thousands of bounce-backs.

Monica Tarazi, New York director of the American-Arab Anti-Discrimination Committee, recently had her personal Yahoo e-mail account shut down for one day for spamming after a message bearing her name was sent to more than 80 Yahoo groups.

Yale medical school professor Mazin Qumsiyeh received dozens of e-mails from irate colleagues after messages he had written to a private list of activists were forwarded to more than 1,500 people in the Yale community without his knowledge.

The content of the impersonated e-mails has varied widely: news accounts of terrorist attacks; historical looks at the relationship between the United States and Jewish people; anti-Semitic rants; pro-Israel analysis. There have even been forged warnings that "the e-mails of the members of this group are hacked by pro-Israeli people."

Earlier this month, Tarazi and Parry discussed the problem with agents from the FBI's computer crimes and civil rights divisions in a half-hour conference call. But the FBI said there was little they could do to stop the e-mail impersonations from continuing.

"While these e-mails are a nuisance, offensive and intimidating, the FBI didn't find anything illegal: There haven't been threats that rise to the level of a hate crime, no money has been stolen, public safety has not been endangered and, as far as we can tell, our computers have not been hacked or 'technically intruded into' as one agent put it," Tarazi said in an e-mail. "The offensive messages are all protected by the First Amendment."