  Smart Contracts (SCs) publicly deployed on blockchain have been shown to
include multiple vulnerabilities, which can be maliciously exploited by users.
In this paper, we present extorsionware, a novel attack exploiting the public
nature of vulnerable SCs to gain control over the victim's SC assets. Thanks to
the control gained over the SC, the attacker obliges the victim to pay a price
to re-gain exclusive control of the SC.
