There comes a point where you claim so much, that people will start looking into it.
I unfortunately had a Marine - a frigging counterpart E6 - who constantly yapped about killing dudes as a prior infantryman in Afghanistan as well as the Iraqi invasion (even while we were deployed together in Iraq). Eventually, he ran his suck so much that his stories crossed, and his facts started to sound fishy... like 'so stupid it can't be real' fishy. I looked into his claims on MOL as I had 1stSgt privileges (that just let me look at everyone's basic record of service - but it includes their original contract information, individual awards, and deployment history)...
...Lo and behold, the dude was never prior infantry. He did do the Iraqi invasion kind of - but his deployment only listed "Kuwait". He was never in Afghanistan. He had never been in combat. In fact, he was wearing a lot of awards that he never earned. I passed the information to the other SNCOs, and we all just F-ed with the dude mercilessly without ever letting him know we were in on his charade. It became a game to us to ask him about his Afghanistan history, and he'd just ramble on and on like this fag in the video above. The junior Marines were told to ignore him.
... Then came the day that my counterpart went to the Career Course (professional school for E-6s), and came back after graduation with an additional 5 ribbons on his chest that he never earned - including a combat action ribbon. That was where we had enough and 'ran him up the flagpole'. He visited the Bn SgtMaj and came back rather sheepish, but no charges. However, he didn't learn his lesson and did the same frigging thing with the extra ribbons and medals for the Marine Corps Ball a few months later. He got photographed and ran up the flagpole again... and somehow got orders out of our Bn within the week.
I don't think anything administrative was ever done to him, which is B.S. He ended up retiring as an E-7, and ironically friend requested a bunch of us on Facebook.
We occasionally will comment on one of his photos with his new wife with an "Have him tell you about Afghanistan".
Just volunteering and serving is duty enough to prove that you have some fortitude as a human being. You don't need to embellish your record to make friends, and frequently you are going to pass off bullshit that is going to raise eyebrows of those who know better. At that point, you get whatever comes your way.