As the London bombings and other recent arrests make clear, Western governments now face the very real threat of homegrown terrorists - undetectable second and third generation immigrants totally assimilated into the societies they want to destroy.
And the so-called "Generation Jihad 2.0" has no need to attend training camps in the hills of Afghanistan since much of the necessary information and propaganda is freely available on the Internet, police and experts said.
"Like the terrorists responsible for both the London and the Madrid bombings, the Toronto suspects lived in the area they intended to attack" FBI Director Robert Mueller said after 17 young Muslims in Canada were arrested in June.
"They were not sleeper operatives sent on suicide missions; they were students and business people and members of the community. They were persons who, for whatever reason, came to view their home country as the enemy", Mueller said.
"These homegrown terrorists may prove to be as dangerous as groups like Al-Qaeda, if not more so."
The Toronto suspects, including five minors, were arrested after purchasing three tons of ammonium nitrate fertilizer, which can be used to create a powerful bomb when mixed with fuel. They allegedly planned attacks in Toronto and Ottawa.
"They are virtually indistinguishable from other youth", said Jack Hooper, deputy head of the Canadian Security Intelligence Service (CSIS). "They blend in very well to our society, they speak our language, and they appear to be, to all intents and purposes, well-assimilated".
Anne Giudicelli from the Paris-based terrorism consulting group Terrorisc said that for terrorism groups it is a "massive coup to have second and third generation recruits, because they have nationality, they are already on location".
"Their activity can be much more effective and more shocking on the ideological front since it demonstrates to Western societies that they can generate enemies from within", she said.
"Jihad leaders' speeches have been put straight onto the Internet for the past year or so - and in English" not in Arabic, Giudicelli added.
In October, London police arrested a young man of Moroccan origin identified as "irhabi 007" ('terrorist 007' in Arabic), one of the most active 'cyber-jihadists', particularly in distrubution of Al-Qaeda propaganda in Iraq.
"Of course, not every extremist will become a terrorist. But the radicalization process has become more rapid, more widespread, and anonymous in this Internet age, making detection that much more difficult", the FBI's Mueller said.
Tackling the homegrown threat is also tricky, added Giudicelli, who recently published a report on the Islamic terrorist threat on Europe for the Franch government.
If a particular community is targeted, there is a risk that this community will be stigmatised and any radicalism will be driven underground, she said.
Anti-Muslim backlash raises fears in US