The threat of Islamic extremism has justice officials balancing tougher law enforcement against the need to protect civil liberties, and that balance is struck in myriad ways around the world. The FBI's collection of demographic data on U.S. communities has drawn criticism from civil liberties groups, while Australia has been accused of reversing the onus of proof by demanding that travelers prove they have legitimate reason for visiting a terrorist hotspot.

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AUSTRALIA

RECENT EXTREMIST ACTIVITY:

— Dozens of Australians are suspected of fighting in the battlefields of Iraq and Syria, then coming home. It's illegal for Australians to fight in foreign militias, but authorities have had difficulty proving such charges.

— Shotgun-wielding Man Haron Monis took 18 people hostage in a Sydney cafe in December; his 16-hour standoff ended when police stormed the cafe. Monis, 49, and two hostages died. In September, 18-year-old Numan Haider was shot dead after stabbing two police officers. Both men had come to authorities' attention before the attacks: Haider's passport had been canceled and Monis was on a terror watch list for a time after writing hate mail to the families of Australian soldiers killed in Afghanistan. The government has ordered an inquiry into why Monis was dropped from the list.

— Australia's main counterterrorism agency, Australian Security Intelligence Organization, says it regularly disrupts terrorist plots.

GOVERNMENT RESPONSE:

— A new law bars Australians from traveling to places the foreign minister declares to be "terrorism hotspots," unless they provide a legitimate reason for visiting. Only one hotspot has been declared: the Syrian province of al-Raqqa, an Islamic State movement stronghold.

— The foreign minister has canceled more than 70 passports of Australians suspected of fighting in Iraq and Syria or attempting to do so, and recently gained the power to suspend passports quickly.

— It has also become easier for authorities to obtain court orders restricting terror suspects' movements and who they associate with.

— Another new law bars anyone who discloses information related to "special intelligence operations," a secret category defined by the attorney general.

— The country plans 630 million Australian dollars ($510 million) in new spending to enhance security over the next four years, including a rollout of biometric screening at airports.

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EUROPE

RECENT EXTREMIST ACTIVITY:

— In and around Paris last week, 17 people and three gunmen were killed over three days of attacks on a satirical newspaper, a kosher supermarket and on police that horrified France and the world. Brothers Said and Cherif Kouachi methodically massacred 12 people at the Charlie Hebdo offices and led police on a chase for two days before they were cornered Friday at a printing house near Charles de Gaulle Airport. Separately, an acquaintance of at least one of the Kouachis, Amedy Coulibaly, shot a policewoman to death and attacked the kosher market, threatening more violence unless the police let the Kouachis go. Near-simultaneous raids at the printing plant and the market Friday left all three gunmen dead; authorities continue to search for accomplices. One of the Kouachi brothers had been convicted on terrorism charges and the other was believed to have linked up with al-Qaida forces while in Yemen, but the French began to view them as less of a threat in recent years. In 2010, Coulibaly was sentenced to five years in prison for an abortive attempt to free another terrorist from prison.

— There have been several other attacks in recent months. In May, a Frenchman linked to the Islamic State group in Syria crossed into Belgium and killed four people at the Jewish Museum in Brussels. In May 2013, two al-Qaida-inspired British extremists hacked soldier Lee Rigby to death on a busy London street.

— Authorities say thousands of Europeans, including about 600 Britons, 550 Germans and 1,200 French citizens have gone to Syria to join extremists there.

GOVERNMENT RESPONSE:

— France ordered 10,000 troops on Monday to protect people at particularly sensitive locations. Interior Minister Bernard Cazeneuve said 4,700 security forces would be assigned to protect France's 717 Jewish schools.

— French Prime Minister Manuel Valls has acknowledged that "a failing" in intelligence led to last week's attack. "That's why we have to analyze what happened."

— Counterterrorism intelligence efforts in western Europe have become more challenging as an increasing number of mostly young Muslims travel to Syria to join forces with the Islamic State group and other militant organizations fighting the regime there. Each country uses a different system to keep track of suspected extremists. Germany does not keep a centralized watch list at the federal level, but the security service of each state maintains lists of people considered dangerous.

— Britain took unilateral steps last week to tighten up its border checks at seaports and train stations.

— Spain raised its terror threat level, not because of a specific plot, but because of a general sense that all of Europe — not just France — was at heightened risk. Spain also stepped up security at transportation hubs like airports and train stations, nuclear power plants, energy networks and water sources.

— At the European Union level, fighting terrorism remains an issue of national governments but the EU has tried, sometimes unsuccessfully, to dovetail those different approaches to improve coordination among its 28 member nations. For three years now, the EU has been discussing a way to increase airline data sharing but so far has been blocked by the EU legislature over privacy objections. In the wake of the attacks, EU leaders have vowed to speed up efforts to reach a breakthrough on the issue.

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UNITED STATES

RECENT EXTREMIST ACTIVITY:

— A twin bombing at the 2013 Boston Marathon killed three people and wounded more than 260 others. Jury selection is underway in the death-penalty trial of 21-year-old Dzhokhar Tsarnaev. Prosecutors say he and his brother, Tamerlan — ethnic Chechens who had lived in the United States for about a decade — carried out the attack in retaliation for U.S. wars in Muslim countries. Tamerlan died in a gunbattle with police. The FBI in 2011 conducted a limited inquiry into Tamerlan Tsarnaev but closed the case after receiving little information from Russian authorities.

GOVERNMENT RESPONSE:

— The FBI, the lead federal law enforcement agency in counterterrorism investigations, is permitted to maintain demographic data on communities within the United States — a process known as mapping that has disquieted some civil liberties groups.

— U.S. counterterrorism capabilities include National Security Agency surveillance programs that sweep up phone records and allow the government to collect communications of non-Americans located outside the U.S. for counterterrorism purposes.

— The U.S. also maintains a no-fly list that bans suspected terrorists from air travel. As of late summer, the list had roughly 48,000 names, including those of the brothers suspected in the Paris attack.

— The New York Police Department has disbanded its Demographics Unit, a team of detectives within the NYPD's Intelligence Division assigned to create databases on where Muslims lived, shopped, worked and prayed. An ongoing review of the division by Police Commissioner William Bratton, who took over a year ago, found that the same information collected by the unit could be better collected through direct contact with community groups. The department hasn't abandoned a practice adopted after the Sept. 11, 2001, attacks of using Muslim informants to try to detect and thwart terror threats.

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CANADA

RECENT EXTREMIST ACTIVITY:

— In October, Canada was hit by two terror attacks by so-called "lone wolves" believed to have been inspired by the Islamic State group. In Ottawa, a gunman shot and killed a soldier at Canada's National War Memorial and then stormed Parliament before being gunned down. Two days earlier, a man ran over two soldiers in a parking lot in Quebec, killing one and injuring the other before being shot to death by police. The man had been under surveillance by Canadian authorities, who feared he had jihadist ambitions and seized his passport when he tried to travel to Turkey.

GOVERNMENT RESPONSE:

— Prime Minister Stephen Harper's government plans to introduce legislation to strengthen anti-terrorism laws, possibly by making it easier to make arrests and detentions.

— The government is also considering giving the Canadian Security Intelligence Service greater flexibility in tracking terror suspects abroad.

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Associated Press writers Colleen Long and Eric Tucker in New York contributed to this report.