SAN FRANCISCO — Facebook has a won US$873 million judgment against a Canadian man who bombarded the popular online hangout with sexually explicit "spam" messages.

The victory, sealed with a judge's order issued last Friday, probably won't yield a windfall for privately held Facebook Inc., whose revenue this year is expected to range between US$250 million to US$300 million.

Court records indicate the alleged spammer, Adam Guerbuez of Montreal, has been difficult to find since Facebook sued him four months ago.

But Facebook is hoping the size of the judgment will scare off other spammers who might be tempted to target the Palo Alto, Calif.-based company's audience of more than 120 million users.

"Everyone who participates constructively in Facebook should feel confident that we are fighting hard to protect you against spam and other online nuisances," Max Kelly, Facebook's director of security, wrote Monday on the company's blog.

Efforts to reach Guerbuez for comment on Monday were unsuccessful.

The case against Guerbuez and his business, Atlantis Blue Capital, illustrates how Internet rogues can manipulate Facebook's communications system to unleash massive marketing blitzes.

According to Facebook, Guerbuez fooled its users into providing him with their usernames and passwords. One method was the use of fake Web sites that posed as legitimate destinations.

After Guerbuez gained access to user's personal profiles, he used computer programs to send out more than 4 million messages promoting a variety of products, including marijuana and penis enlargement products, during March and April of this year, Facebook said.

"Despite the resources dedicated to spam eradication, current available technology does not permit Facebook to completely prevent the transmission of spam on its site," the company's lawyers wrote in the case against Guerbuez.