This should be a trivial problem for anyone who is properly managing his or her Bitcoins. A group called the “Large Bitcoin Collider” claims it can smash open bitcoin wallets by using a so-called brute force attack, which directs mass amounts of computer power at individual wallets in order to guess their private keys.
A “trophy list” on the home page of Collider (an apparent reference to the Hadron Collider) suggests the group has successfully opened over a dozen wallets, though only three had any Bitcoins in them.
You can read more in an article in the Fortune web site at http://fortune.com/2017/04/15/bitcoin-collider/ although that article appears to be written by someone who doesn’t know much about Bitcoins.
The ‘Large Collider’ Attack appears to only work on Bitcoin wallets that store their information online or in a cell phone or tablet computer. Indeed, there are dozens of such wallets for Android, Apple iOS, Windows, Macintosh, and Linux systems. Online wallets are very convenient to use and are apparently quite popular. However, only a Bitcoin novice will ever store a significant number of Bitcoins in an online or cellphone wallet.