Any one know how to open this screw?
Tried pliers but no avail and standard box of security screwdrivers couldnt open it.
Here are some more photos
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Those are external line head screws, and are used as anti-tamper screws in some Japanese electronics. You can probably find a driver for them from a game console hack supplier (they're used on Gamecube, Wii, and some other game consoles). The driver looks like this (sorry for the horrible pic):
They also come in 5 and 7 point varieties (hard to tell how many points from the picture you posted). I've also seen them called torx inverted.
If you don't want to get a specific driver for them, you can probably get them out by clamping on the head really hard with a pair of vise-grips or use a screw extractor. You might be able to find a socket that will mesh with them well enough, but that's a long shot.
If it's a screw, a couple of ideas:
It looks like a rivet, in that case you will have to cut it off or try to pry the head off.
It also looks like it has 6 tabs, you might be able to get a 6-sided socket on it and break the head.
You can use a pipe wrench for this. If you use it "downwards" the wrench tightens itself on the screw. It is a little tricky because you have to make sure the wrench stays on the screw of course.