A side channel attack, as described in the scenario, involves an attacker using indirect methods to gather information from a system. In this case, Alice is exploiting the shared physical resources, specifically the processor cache, of a virtual machine host to steal data from another virtual machine on the same host. This type of attack does not directly breach the system through conventional means like breaking encryption but instead takes advantage of the information leaked by the physical implementation of the system, such as timing information, power consumption, electromagnetic leaks, or, as in this case, shared resource utilization, to infer the secret data.