Given the first direct detections of gravitational waves (GW) from a binary coa- lescence, the first tests of General Relativity (GR) using these data became possible. Among them there is the proposal that aims to verify the existence of event horizons around black holes (BH). This recently proposed test, came to be after the argument that GW emitted by the colisions of horizonless compact exotic objects (ECO) with no central singularity differs from the ones emitted by black holes by the existence of repited pulses after the signal predicted by GR. Such pulses have been referred as echoes in the literature. Motivated by quantum gravity arguments, such as the prediction of firewalls as a solution for the information paradox, ECOs provide a clear motivation for a search for deviations in GW observations. The project described here can be divided into two parts: the first seeks a theoretical understanding of the echoes phenomenology, which has been widely explored by the student in the first years of the his PhD program; the second part, currently under development, intends to apply the knowledge acquired previously to perform a search for possible echoes in the data of the LIGO/Virgo Col- laboration. This qualification exam intends to demonstrate that during the first part of the project, influences of the orbital movement and the binary mass ratio were found in the echoes not previously reported in the literature. It is also intended to show the echo search strategies that are being studied to investigate the existence of evidence of echoes in the available data, and thus test the validity of the GR and constrain the amplitude of echoes.