BEIJING (Reuters) - Hu Ziwei looks harmless enough but she set security alarm bells ringing in China last December when she crashed the launch of state broadcaster CCTV's Olympic channel to accuse her sports anchor husband of infidelity.
Hundreds of thousands of Chinese saw footage of the incident on the Internet, alarming a government concerned that unpaid workers, evicted home owners and other people with grievances might try to emulate her by washing their dirty linen on live television during the Beijing Olympics.
"Factors of instability will be difficult to guard against because it cannot be predicted where they will be," dissident writer Liu Xiaobo said.
Activists unfurling banners, medalists making political statements, bomb scares, prank calls, contaminated food and water and North Korean refugees scaling embassy walls are all possible threats to the image China hopes to project through the Games.
But China's gravest concern is terrorism.
Such violence at previous Games tends to support their concern.
A bomb at the 1996 Atlanta Olympics killed one person and wounded more than 100, while at the 1972 Munich Games 11 Israelis died in an attack by Palestinian gunmen and botched rescue attempt.
China has not publicly stated which groups might target the Games, but clearly Uighur militants from the restive Xinjiang region in the far west are seen as a major worry.
A senior Chinese official has warned that Uighurs agitating for an independent "East Turkestan" in the predominantly Muslim region were plotting attacks on the Games.
The Beijing Olympics are "a prime theoretical target for al-Qaeda and other terrorist groups," Interpol said on its Web site (www.interpol.int).
"The absence of a terrorist incident and serious criminal activity will be an ... important measure of the success of these Games," Interpol Secretary-General Ronald Noble told a security conference in Beijing last September.
In January, police shot and killed two "terrorists" in Xinjiang and detained 15 others. Five policemen were wounded when hand grenades were hurled at them.
Security will be tightened around Beijing and other entry points to China. Underlining Beijing's actions, a security zone will be set up around the city's international airport to prevent aircraft being shot down.
With about 60 heads of state, including U.S. President George W. Bush, descending on the Chinese capital for the Games, Beijing will need all the help it can get to ensure a safe Olympics.
Xi Jinping, heir apparent to President Hu Jintao, has been put in charge of Olympic preparation, one of the toughest jobs in China.
Interpol has shared "crime-related information such as the names, fingerprints, photographs, DNA profiles, criminal modus operandi of those who might wish to kill or harm."
The world police organization has also designed its most ambitious passport and visa application screening process to identify stolen, lost and fraudulent travel documents and suspected terrorists.
The International Atomic Energy Agency is also helping Beijing guard against any potential attack at the Olympics by providing nuclear detection equipment and training staff in its use.
Last month the head of the U.S. Federal Bureau of Investigation gave Beijing's security preparations the thumbs up, while also offering China help against potential threats.
Chinese organizers have also sought advice from the security chiefs of the two previous Summer Olympics but for manpower they will be relying on their own people.
Some 100,000 policemen and 600,000 volunteers will patrol venues, hotels and streets, while neighborhoods will be manned by citizens wearing red armbands. A network consisting of about 300,000 surveillance cameras covers the entire capital.
By using on its own security forces, Beijing believes it can deliver a secure Games for $300 million, or a fraction of the $1.8 billion that Athens paid in 2004. Then, NATO forces were closely involved in the first Summer Games post the September 11 attacks.
The government has already banned the flying of model planes in parts of the city to thwart any plot to scatter anti-China leaflets. It has tightened controls over the transport of explosives for use at mines to prevent theft.
To ensure the world sees and hears no "evil" at the emerging global power's coming-out party, police have also detained AIDS activist Hu Jia and dissidents perceived as security threats.
But with 30,000 media in town, any heavy-handed tactic to silence protesters could be a public relations disaster for China.
Other potential party poopers include adherents of the outlawed Falun Gong spiritual movement.
"Falun Gong is seen as one of the biggest threats to the Communist Party in the run-up to the Olympics," said Nicholas Bequelin, Hong Kong-based researcher for Human Rights Watch.
The group is a perennial headache for China. A heckler disrupted President Hu's White House appearance in 2006. China is also worried Falun Gong might hijack satellite signals to disrupt state television broadcasts.
Additional reporting by Guo Shipeng and Lucy Hornby; Editing by Nick Mulvenney and Jeremy Laurence