![]() ![]() Private static async Task ReadFileAsStringAsync(string path) Private static readonly Dictionary MorseCodeDict = new Dictionary Thread.SetApartmentState(ApartmentState.STA) Var pBytes = Convert.FromBase64String(b64) Var b64 = MorseEncoder.Decode(res).Result You might think of your own encoding dictionary! using System This is just a simple demonstration on how to encode characters using the dots and dashes. The following is the complete code for our test program, including the Encoding & Decoding functions. Our Entropy analysis aligns with the results described in Figure 2! The Morse Code Encoder – Figure 5 shows the results of the entropy analysis for a PE file that has an embedded PE encoded in Morse Code. ![]() Figure 4 shows the results of the entropy analysis for a PE file that has an embedded PE encoded in Base64. We can see that the sample that used Base64 has a 5.781 Entropy score, and the one that used Morse code has a 2.572. Here are the results for two different PE samples, one with an embedded PE resource encoded as a Morse Code and another sample embedded and encoded as a base64. We can calculate the Entropy score using the sigcheck.exe utility that comes with the Microsoft Sysinternals Suite: > sigcheck.exe -h -a FILE_PATH NET Loader – code snippet Calculating the Entropy Score Load and Invoke the assembly bytes in memory.Decode the content of the file from Morse code to Base64.Read the content of the embedded file “mc”.In the code snippet below, we can see that the program is loading a Morse code from an embedded resource, then decodes it and executes it in memory. NET PE that loads and executes an embedded PE that has been encoded using Base64 and Morse code. The scenario described in this article is that we have a. The primary goal here is to reduce the entropy level. Figure 2 shows the results of the entropy analysis for the sample sets described in Reducing Entropy level using Morse Code Figure 1: Histogram of entropy of legitimate versus malicious files. Īs it turns out, malware authors also tend to rely heavily on packing, compression, and encryption to obfuscate their tools on order to evade signature based detection systems. The less duplication there is in a file, the higher the entropy will be because the data is less predictable than it was before. The end result is a file with less duplicated contents. Compression algorithms reduce the size of certain types of data by replacing duplicated parts with references to a single instance of that part. Each of the previously mentioned techniques tends to increase the overall entropy of a file. Shannon entropy can be a good indicator for detecting the use of packing, compression, and encryption in a file. How does Entropy analysis apply to intrusion detection? This is a specific algorithm that returns a value between 0 and 8 were values near 8 indicate that the data is very random, while values near 0 indicate that the data is very homologous. When referenced in the context of information theory and cybersecurity, most people are referring to Shannon Entropy. The code is depicted in the following table : Letters – AĮntropy is a measure of randomness within a set of data. The International Morse Code encodes each letter of the basic Latin alphabet, each of the Arabic numerals and a small set of punctuation and procedural signals (prosigns) as a sequence of short and long electrical pulses referred to as “dots” (short) and “dashes” (long) or “dits” and “dahs”. Samuel Morse developed the initial facets of the code which bares his name but others contributed to the code as it now exists. The code has also found wireless applications using signal lamps and audio devices and has also been used in long range radio communications and radio navigation applications. Morse Code is a communications “language” that was initially developed for transmission of letter by letter textual information by wire using the telegraph system. Primary Keywords: Binary Entropy analysis | Evading Static Analysis | Morse Code Encoder What is Morse Code? This article demonstrates reducing the Entropy score with a goal of evading the static detection by encoding characters using only dashes and dots. Reducing Entropy level using Morse Code.How does Entropy analysis apply to intrusion detection?. ![]()
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