receive the signal via a bus of the bus system;

ascertain, using a measuring device, a first variable that characterizes a length of a bit sequence associated with the signal, the bit sequence including n bits, where n is greater than or equal to one, wherein the length of the bit sequence is a time duration of the bit sequence, wherein the measuring device includes at least one of the following elements: A) a time-to-digital converter, B) a hardware circuit, C) an application-specific integrated circuit (ASIC), D) an analog-to-digital converter; and

ascertain a second variable that characterizes a deviation of the length of the bit sequence from a reference bit sequence that includes n bits, wherein the length of the reference bit sequence is a time duration of the reference bit sequence;

measure, using the measuring device, a time duration of a first time period between a rising edge of the bit sequence and a next, falling edge of the bit sequence following the rising edge,

measure, using the measuring device, a time duration of a second time period between a first rising edge of the bit sequence and a next, rising edge of the bit sequence following the first rising edge,

measure, using the measuring device, a time duration of a third time period between a falling edge of the bit sequence and a next, rising edge of the bit sequence following the falling edge,

measure, using the measuring device, a time duration of a fourth time period between a first falling edge of the bit sequence and a second falling edge of the bit sequence following the first falling edge;

ascertain a first piece of information that characterizes a sender of the bit sequence based on the first variable and the second variable, wherein the first piece of information that characterizes the sender of the bit sequence is further based on the time duration of the first time period, the time duration of the second time period, the time duration of the third time period, and the time duration of the fourth time period, and wherein the first piece of information is a fingerprint characterizing the sender;

detect an intrusion on the bus system based on the first piece of information; and

initiate a countermeasure based on the detecting of the intrusion.