Pressing again and again actually works for once times. This was happended of two security researchers in Spain, they found bug on Linux computer just by pressing the backspace button 28 times.
This time, the issue is neither in a kernel nor in an operating system itself, but rather the vulnerability actually resides in Grub2, the popular Grand Unified Bootloader, which is used by most Linux systems to boot the operating system when the PC starts.
The scientists, Hector Marco and Ismael Ripoll from the Cybersecurity Group at Polytechnic University of Valencia, observed that it's conceivable to sidestep all security of a secured Linux machine by misusing a bug in the Grub2 bootloader. Basically, hitting delete 28 times when the machine requests your username gets to the "Grub salvage shell," and once there, you can get to the PC's information or introduce malware.
HowTo secure Your Linux Computer: