Computer forensics expert Gary Warner says there's heavy activity in hacker chat rooms from groups angered by Osama Bin Laden's death.
Warner, from the University of Alabama, says he's reviewed thousands of messages, looking for news of planned attacks.
So far, he says, he’s found heavy activity among three groups: Jihadi groups without a 'cyber' component; pro-Palestinian groups that haven't in the past been linked to Al Qaeda; and Arabic-language hacker groups.
Among the Jihadi groups, Warner says he's seeing "mostly very pious, very religious expressions of sorrow and mourning; prayers for Bin Laden and his friends and family".
The pro-Palestinian groups are discussing a series of hacker attacks timed loosely for the May 15 anniversary of their first intifada - and which were already being planned before Bin Laden's death.
And Arabic-language hacker sites are posting messages declaring allegiance to bin Laden's cause, along with poetry - "the golden lion has left us and there is a black place in our hearts", and the like - but are also, ominously, promising to "pick up the banner of Jihad".
"Things are a bit confused right now by the fact that there has been very active planning in the pro-Palestinian hacker movement for events surrounding the anniversary of the first intifada," says Warner.
"Many Israeli websites are being attacked, but this activity began before the announcement, and is likely to continue to increase leading up to May 15, a day that some are declaring ‘the 3rd Intifada."
He says he'll continue to monitor the groups.