Anti-Israel protests in 'Second Life.'
A Twitter feed about the conflict in Gaza.
A Facebook group for Americans to protest Israel's offensive in Gaza.
Joel Leyden founded a Facebook group to discuss the conflict between Israel and Hamas.
A shadow war between pro-Israeli and pro-Hamas forces is taking place on the Internet — and it is getting fierce.
If you're one of millions of Americans who use social-networking sites such as Facebook and Twitter or participate in virtual worlds like "Second Life," don't be surprised if you get sucked into a war thousands of miles away in Gaza.
Support groups have sprouted up on Facebook, drawing in thousands of members on both sides of the conflict. Protests erupted in "Second Life"'s virtual Israel, where demonstrators showed up to voice support for Hamas and the Palestinians.
People are using Twitter updates to tell the world what they're witnessing on the ground or how they feel about the news. And videos of the carnage in Gaza have been posted on YouTube, including some from the Israeli government.
On Facebook, the pro-Hamas group "Stop Genocide in Palestine" has more than 117,500 members. On the other side, "I Support the Israel Defense Forces in Preventing Terror Attacks from Gaza" has more than 65,000 members.
Some Facebook users have changed their profile pictures to Israeli or Palestinian flags, bloody images of war or other partisan graphics to get their messages across.
Facebook users can use applications to set messages in their status bars expressing affiliation with one side or the other. An application called "Qassam Count" enables users to voice their support for Israel by automatically updating their status bar when rockets are fired from Gaza into the Jewish state.
Joel Leyden, an American working in Israel, said he founded the "Support the Israel Defense Forces in Preventing Terror Attacks from Gaza" group to give members a place to voice their opinions and grievances about the conflict.
"Facebook, as we all know, was created by a university student for university students, and it's turned into the number one watering hole for the international community," Leyden said. "That can't be better illustrated than how it's being used today with the war here that we have with Hamas."
Thousands of messages have been posted to the group. Moderators watch over the conversation in Israel, Europe and North America.
Leyden said he's received dozens of death threats since he started the group.
"I've served in [the Israeli army] in combat and in the spokesperson's office and with the border police," he said. "I've never felt more in a dangerous environment than I do here. Everyone is trying to make as much noise as they can to break through."
Messages like "death to the Jews" and "we can't wait to murder you" have been posted to the group, he said, but since positing pro-peace messages to the site in Arabic, Leyden said things have toned down considerably.
None of the pro-Palestinian groups on Facebook responded to a request for comment.
The operators of Facebook, meanwhile, are taking pains to ensure that the online war doesn't get out of hand.
"We are sensitive to and subsequently take down Groups that threaten violence towards people. We also remove groups that express hatred towards individuals and groups that are sponsored by recognized terrorist organizations," Linder wrote.
Facebook on Thursday removed a Web site called "Hitler Took the Right Decision With Jewish People," saying the group violated its policies.
"We want Facebook to be a place where people can openly discuss issues and express their views," Linder wrote. "As such, we do not aim to control the discourse on Facebook.
"Rather, we take swift action to remove content that violates our policies. Our goal is to strike a very delicate balance between giving Facebook users the freedom to express their opinions and beliefs, while also ensuring that individuals and groups of people do not feel threatened or endangered."
In the virtual world "Second Life," SL Israel saw protests from virtual pro-Palestinian activists when the violence in Gaza flared up.
"Lots of people yelling," the founder of SL Israel, who goes by Beth Odets in the game, told Second Life blogger Wagner James Au. "They were going on and on with slurring obscenities about murderous Israeli forces, etc."
Odets began ejecting the most offensive protesters from the area, she told Au.
"I had to be careful not to boot people who didn't actually do anything wrong," she said.
She temporarily had to close SL Israel to outsiders to quell the protests, but protesters kept coming. Eventually, however, people came who wanted to talk.
Twitter user Ahuvah Berger, who lives in Israel, said she has been using the network to update her contacts about terrorism for years.
"I believe it is very important to help get our side of the story using a medium in which I already have a large audience who 'know' me," she wrote in an e-mail to FOXNews.com.
"As we know Israel is not good at PR, and as the perceived aggressor it needs to show the world why it does and continues to do what it feels necessary to protect its citizens," she wrote.
"I have encountered a lot of nasty Twitter users who believe in their own propaganda and when confronted with facts, not only facts emerging from Israel, they resort to calling me a Nazi and a perpetrator of a Palestinian holocaust."
Ron Kutas of Stand With Us, a pro-Israel group, said taking the war onto the Internet has its problems.
"It's opening up the door to anybody who wants to say anything," Kutas said. "It's very hard for people to distinguish between emotional commentary about the conflict and factual journalism about the conflict ... you have an open forum and people who are not educated about the conflict are being told misinformation all the time."
Kutas said he uses Qassam Count to spark discussion with friends who oppose Israel's actions in Gaza.
"People who I'm friends with who have opinions that are not the same as mine, we have dialogues about real issues and real facts. When that happens it's a great thing," he said.
Asked if any of his friends had chosen not to associate with him on Facebook because of his pro-Israel activism, Kutas replied, "I don't know of anything of that sort, but I should look into that."