The situation when an illegal user intercepts data from the communication channel of two legal users is considered. The data in the legal channel is protected from distortion by error correction codes. It is assumed that the intercept channel may be noisier than the legal channel. And, consequently, the interceptor receives low-quality data. The possibility of using a special type of error-correction code decoders by an illegal user to restore damaged data is discussed. The interceptor model is constructed. The model includes a receiving block of the intercept channel, as well as several auxiliary blocks, such as a memory device, a block for determining the quality of communication in the legal channel, databases with possible decoders and their parameters. Examples are given that show the potential capabilities of the interceptor. The examples demonstrate the difference in decoding quality between different decoders for LDPC codes and Reed-Muller codes. These examples show that an illegal user with the various decoders described in the open press can receive information with satisfactory quality even at a weak signal level in the intercept channel. The constructed model can be useful in the tasks of developing methods of protection against intruders who organize illegitimate data interception channels.