Vulnerabilities
Cylinder locks are vulnerable to a technique known as "lock snapping" also known as "cylinder snapping", where force is applied to the lock until it breaks into two pieces. The attack exploits the fact that a double cylinder lock is inherently weak in the centre. The attack typically takes between 50 seconds and 2 minutes. In February 2012 West Yorkshire Police revealed that 27% of all burglaries in the county used this technique.
To overcome the risk of "lock snapping", several lock manufacturers have developed higher security Anti-Snap cylinders. These security cylinders typically feature Anti-Snap lines and are British Standard Kitemark and Secured by Design approved. The Anti-Snap lines act as sacrificial points, meaning that if force is applied to either end of the cylinder it will break away only to the Anti-Snap line, leaving the mechanism inside the door intact - allowing the correct key to still operate the lock.
Groove-and-spring cylinder locks are vulnerable to tooth-taping. This technique involves a pick, which is a thin piece of hard steel with a small hook at its end, and some other tool that can be inserted into the keyhole alongside the pick and used to rotate the cylinder. The technique relies on small imperfections in the cylinder, that lead to a single tooth is holding the cylinder from rotating. The burglar applies constant (though weak) torque on the cylinder, and tries the pick at each tooth. When the pick fiddles with the tooth that actually holds the cylinder, the cylinder will rotate minutely, until another tooth will stop it. Now the first tooth is held in open position by the cylinder itself, and the burglar can proceed to pick the other teeth. Though these principals are easy to understand, in practice a great deal of experience and patience is required in order to master this technique. Very high quality cylinders are less prone to this attack, requiring more time as well as superior skill, however, electronic locks are far cheaper and robust just as well.
Similar concept is utilized in powered picks. This appliances require no skill to operate, but are noisy so its usefulness for criminal use is limited. The powered pick uses multiple picks simultaneously, which are bounced very rapidly, and within minutes a common cylinder yields.
Read more about this topic: Cylinder Lock