They all can be undone, just like anything else can be possibly broken given enough time, determination and the right tools. The idea is not to prevent the theft entirely, because it's not possible, but to make it a little more time consuming and more involving, so the thief may think twice. I have skewers with regular hex bolts. They take significantly longer to undo that regular quick release skewers and you need to have a tool on you. That lowers the chances of theft of opportunity, but won't stop a prepared and determined thief.
Many security bolts can be undone with flat screwdrivers with enough skill.
Originally Posted by
lungimsam
I have quick releases with levers that lock.
No tools necessary. They look and are just like QR's, but they lock when the bike is upright.
Simply flip the bike upside-down and they unlock and you can flip the QR levers open and pull out the skewers like a regular QR.
Then just insert your regular QR's.
Zefal locking skewers.
http://www.zefal.com/en/locks/81-lock-n-roll.html
That is very interesting.