By Richard Allen Greene
BBC News, Washington
The Pentagon is keeping a close eye on what its troops post online, with special attention being paid to videos that show the aftermath of combat.
Some websites exist specifically in order to post gruesome videos
There is no specific policy that bans troops from posting graphic material.
But troops who have served in Iraq and Afghanistan are hearing the message that they should consider carefully what videos they upload to the web.
Sites such as YouTube and Ogrish.com have hundreds or thousands of clips from soldiers, some set to rock music.
At their most graphic, they show the aftermath of suicide bombings and gunfights between coalition forces and insurgents.
Many include troops using foul language.
One soldier who served in Iraq in 2005 told the BBC there was "a tight watch" being kept on video and pictures posted to MySpace, with civilian contractors monitoring the internet on behalf of the Pentagon.
The BBC has not been able to confirm that contractors are scouring the internet for inappropriate material from the military.
But US Central Command - which is responsible for troops in Iraq and Afghanistan - does have a team reading blogs and responding to what they consider inaccuracies about the so-called war on terror.
Some troops just want people to know what they have been through
And a longstanding military public affairs officer in Iraq said the Pentagon is also worried about some of the images that are appearing online.
"There's continuing concern about the use of these videos and stills being used by our enemies to propagate the false notion that our military members are barbaric, warmongers - which is unequivocally not the case.
"And... many of these videos and photos can harm force protection and operational security measures."
Ward Carroll is the editor of Military.com, which has a section called Shock and Awe where combat videos are posted.
One of the most popular is called Hostile Demise.
In it, US forces watch what seem to be insurgents depositing weapons in a field, discuss what to do and then get permission from their commander to shoot three people dead and destroy their two vehicles.
"It's very graphic. At some level, it's a view of what happens when you pull the trigger," Mr Carroll, a former Navy officer, told the BBC.
"It's sobering, it's energising, it can be off-putting."
'War is grotesque'
He said the US Department of Defense would prefer that his website not have such videos.
"The military has an interest in its reputation and its image. When the popularity of these prurient, violent videos starts to eclipse their ability to control the image, then a concern arises."
Military.com exists to celebrate the military, he said, and would never post a video showing dead Americans or innocent bystanders.
"We have had stuff submitted where you could see the aftermath of the explosion. We ruled that has no value in our mission," Mr Carroll said.
But such images are precisely the mission of Ogrish.com, according to co-owner Hayden Hewitt.
"There is a distinct misapprehension in the West about what war is like. They think it's a gentlemanly thing. People have forgotten how grotesque war is."
Mr Hewitt estimated that his website has about 1,000 separate items from Iraq - many more from insurgent websites than from coalition forces.
He said he did not know how many coalition troops had posted video to his site.
But he said it was clear to him why they did so: "Some people don't want infamy or fame. They just want people to know what they have been through."
And he said no policy would stop service members from posting material online if they were determined to do so.
"Clamping down is probably a very bad move," he said.
One soldier who posted a video summarising his tour of duty in Afghanistan agreed.
"I don't remember them telling me not to post anything but I'm pretty sure I'm not supposed to," said the veteran, who asked to be identified only as Mike.
"But I posted it when I got out of the military. I'm not sure if I would have posted it or not if they told me not to."