A Chinese anti-virus company has warned against free downloads of Ang Lee's steamy spy thriller, Lust, Caution, saying several hundred sites offering the service were embedded with viruses.

And Chinese doctors have warned moviegoers not to try some of the more ambitious sexual positions featured in the uncut version of the film.

The movie has been a big hit in China, reaping 90 million yuan ($12.12 million) in its first two weeks, despite losing seven minutes to the censors, and has been tipped by some to be the year's biggest box office success.

People should be wary of Web sites that offer free downloading services because their personal passwords can be stolen, Li Ting, of Rising International Software Co. Ltd., told Reuters.

She said several hundred Web sites promoting Lust, Caution were embedded with viruses and 15 percent of download links were contaminated.

Hackers are taking advantage of popular entertainment hotspots for movies and music to attack personal computers and spread viruses, she said.

An engineer with the company was first to encounter the virus last week -- his screen went blank and he lost his instant messaging password.

Set in World War Two Shanghai, Lust, Caution, features long and sometimes violent sex scenes that director Lee has hinted were real.

Lee, who won the best director Oscar in 2005 for his controversial gay cowboy drama Brokeback Mountain, personally cut on-screen sex and other scenes in Lust Caution to allow it to pass Chinese censors and screen on the mainland.

The cuts, however, prompted a flood of Chinese moviegoers in southern China to cross the border into Hong Kong to see the full version.

Chinese doctors warned moviegoers not to try some of the more acrobatic positions featured in the uncut movie, according to a report posted on Xinhuanet (www.xinhuanet.com), a news portal for the official Xinhua news agency.

Most of the sexual maneuvers in 'Lust, Caution' are in abnormal body positions, the report quoted Yu Zao, a deputy director at a women's hospital in southern Guangdong province, as saying.

Only women with comparatively flexible bodies that have gymnastics or yoga experience are able to perform them. For average people to blindly copy them could lead to unnecessary physical harm, Yu said.

Lust, Caution won the Venice Film Festival's top award, the Golden Lion, earlier this year.

($1=7.427 Yuan)

(Reporting by Beijing newsroom; editing by Nick Macfie)