A method and system for mitigating a propagation of a file that includes malicious code. Segments of the file are determined by a series of sizes determined by a function ƒ. Signatures identifying segments of the file are determined by applying a hash function to each segment. A complete match between the file and a malicious file is determined by determining a first match between signature(s) identifying a first set of segment(s) of the file and signature(s) identifying corresponding segment(s) of the malicious file and by determining a second match between a signature identifying a final segment of the file and a signature identifying a last segment of the malicious file. Responsive to determining the complete match, the file is identified as the malicious file and a transfer of the final segment of the file is interdicted.