The Syrian Electronic Army (SEA) has posted a series of photos on the US Marine's website purporting to show soldiers in uniform holding up written messages protesting US involvement in Syria.
In one image, a male appears dressed in full military uniform holding a piece of card in front of his face which reads: "I didn't join the Navy to fight for Al Qaeda in a Syrian civil war."
Efforts to find out more about the mystery marine have focused on the brightly coloured ribbons on his chest. It has been suggested that one of them is a Kuwait Liberation Medal from the first Gulf War. If correct, the protester would be an older marine because that conflict ended 22 years ago.
It is also possible the man in the image is a retired member of the Navy who donned his uniform for the protest. Another possibility is that he is not a Navy marine at all, but is simply dressing up.
The image has drawn criticism as well as praise on the web. Some users have accused the protester of being a coward by appearing ready to break a marine's legal and ethical duty to follow orders, regardless of his personal opinion on the action being taken.
Writing on the website 'This ain't Hell, but you can see it from here,' Jonn Lilyea said: "One thing that should be abundantly clear is that you swore to obey the orders of the President and the officers appointed over me according to the uniform code of military justice."
In an email interview with the BBC, an SEA spokesman warned media outlets reporting on the conflict in Syria to "expect us" and that the group had "many surprises" planned.
He added: "Military intervention in Syria has many consequences and will affect the whole world. Our main mission is to spread truth about Syria and what is really happening."
The Syrian Electronic Army (SEA) has been highly active over the last six months targeting media outlets it believes are reporting untruths about what is happening in Syria. The group, which supports President Bashar al-Assad, last week claimed responsibility for attacks on the New York Times and Twitter - as a result of the group's official Twitter account being suspended.