Written Information Security Policy (WISP). Listing 10.Setting up the return value of the decryption function (the size of the decrypted data) as well as any other final values we wish to place in registers. When all your preparations and protections fail you, having cybersecurity insurance to help you recover quickly and effectively can mean the difference between a complete failure of your company and just a bad year. All the above algorithms are extensively documented, and implementations can easily be found for many programming languages. Imagine a threat that can adapt to every form of defense you throw at it, a threat that constantly changes to avoid detection, a threat that is relentless. Once in a while I will send a free newsletter with: If you're interested in software protection technologies, cryptography & reverse engineering — give it a try! In the case of RSA, cracking the public key involves splitting it into its two prime factors (RSA public keys are the product of two very large prime numbers). But fast-changing polymorphic malware now makes up an overwhelmingly large percentage of the malware organizations are facing. Our algorithm will use a randomly generated encryption key, but to prevent the key appearing directly in the code, we will encrypt it with a second, random key. Code Issues Pull requests Defund the Police. Blocks of code decrypt the virus instruction-by-instruction and push the decrypted instructions to the stack. • The idea is to encrypt the code with a random key and decrypt it at runtime. It has the potential to contaminate your data by writing certain malicious codes. Our decryption function will return a value of type DWORD (a 32-bit value corresponding to unsigned int), which indicates the size of the decrypted data. signature-based identification programs. To enable polymorphic code, the virus has to have a polymorphic engine (also called mutating [...] engine or mutation engine) [...] somewhere in its encrypted body. Alignment between functions is normally achieved with the 1-byte instruction nop (no-operation) or int3 (an interrupt for the purpose of trapping into a debugger). Un virus polymorphe est un virus informatique qui, lors de sa réplication, modifie sa représentation, ce qui empêche un logiciel antivirus de l'identifier par sa signature. Using the pseudoinstructions we generated earlier and which we used to encrypt the data, we will now generate instructions which perform the encryption process in reverse, and place them in a loop that repeats this process on each input block. Two other polymorphic viruses by the name of Tequila and Maltese Amoeba appeared in … A similar technique is also used in debugger detection, where the fnstenv instruction will reveal that the most recently executed FPU instruction is not part of our program, but refers to some other FPU instruction, which is directly or indirectly executed by the debugger. Pour activer le code polymorphe, le virus doit avoir un moteur polymorphe (aussi appelé [...] mutation du moteur ou de mutation [...] du moteur) quelque part dans son corps crypté. Listing 13.Correcting the address of the encrypted data in previously generated code. Thanks to this, the library can be used to target code for 32- and 64-bit environments. We take advantage of the fact that this instruction stores a return address on the stack before jumping to a chosen memory address. This allows someone who has a normal … Another reason for the attraction is that polymorphic code is harder for researchers to pick apart and track down its shifting series of operations. In our case, we work out the location of our "encrypted" data by adding the number of bytes between the delta_offset: label and the end of the function. Listing 15.Definition of the polymorphic engine class. References in periodicals archive ? Imagine a threat that can adapt to every form of defense you throw at it, a threat that constantly changes to avoid detection, a threat that is relentless. Cependant, ces virus sont dangereux et peuvent détruire votre ordinateur. By building a robust, defense-in-depth cybersecurity program as outlined above, you create an equal playing field where the hackers do not have the upper hand. Make sure you install all system and software updates to everything. fugenit.co.za. In this case, we are referring to unique, dynamically-generated code (i.e. A Polymorphic Virus is a type of ‘shape-shifting’ virus, producing malicious code that is able to replicate itself with new signatures but identical payloads over and over again. Education. The registers used for decryption, for holding a pointer to the encrypted data, and for holding a pointer to the output buffer, will be selected randomly each time the decryption routine is generated. In this article, we will cover all the steps necessary to create a simple polymorphic engine, which will serve to encrypt any supplied data, and generate a unique decryption procedure, with the encrypted data embedded within it. Sign up with CyberHoot today and sleep better knowing your. Otherwise, the operating system's protection mechanisms, like e.g. Polymorphic code was the first technique that posed a serious threat to virus scanners. The first known polymorphic virus (1260) was written by Mark Washburn in 1990. Instructions which access memory are faster if the data they read or write is aligned, i.e. Par conséquent, n’utilisez pas ce virus à des fins malveillantes. Polymorphic Code Kamran Sharief, 3 months ago 0 . This is the stark reality of the threat the polymorphic virus poses to your computer systems and personal data. • Polymorphic viruses randomly encode or encrypt the program code in a semantics-preserving way. (You can also recognize an infected file by the string "-----this is silly python virus-----" which is printed whenever the infected program is executed.) This makes it possible for the function to output extra values. The first recorded polymorphic engines date back to the year 1990. Already in the days of MS-DOS, some computer viruses were encrypted by their creators in order to evade detection by antivirus software. Home > Education > Polymorphic Code. It can constantly create modified versions of itself to avoid detection but retain the same basic program after each infection. The first type are block cipher algorithms (data is encrypted in blocks of fixed size), including: There are also stream cipher algorithms (which encrypt data one byte at a time), such as the popular RC4 algorithm. Now that the entire code of the function has been generated, we can write out the encrypted data block, so it will follow the code of the function. The return address generated by call delta_offset will refer to the next instruction, in this case pop ebp. It depends on the use of the call assembly instruction, normally used to call a function. Soon, virus creators developed decryption algorithms whose code was uniquely generated every time, which allowed viruses to be created which could not be detected using static signatures. PPE-II – Prizzy Polymorphic Engine (by Prizzy) – a polymorphic engine which exploits MMX and FPU code, as well as intentional brute-force calculations in its code, so as to slow down operation of emulation strategies used by antivirus software; In most cases, this type of encryption was used in executable file infectors. At the start of the decryption function we will load the encrypted key into regKey, and then decrypt it. in the Metasploit framework. This way, traditional security solutions may not easily catch them because they do not use a static, unchanging code. The polymorphic engine of the virus implements a build-and-execute code evolution. The encrypted data is located just after the end of the decryption routine, and we don't know its address in advance either. computer instructions). Each new polymorphic requires its own detection program. Related Terms: Macro Virus, Memory-Resident Virus, Melissa Virus. Sound simple? This is the stark reality of the threat the polymorphic virus poses to your computer systems and personal data. Listing 4.Obtaining the current code address through the use of the delta offset technique. This technique has its roots in computer viruses. Encryption is the most common method to hide code. In order to change its physical file composition during each infection, the polymorphic virus encrypts its code and adopts a different encryption key each time. This polymorphic botnet contained at least 12,000 compromised computers and was able to change itself up to 19 times a day to avoid detection. Our dynamically generated code can be located anywhere in memory and launched from there (assuming the memory region has the appropriate executable flags set). Now that you have seen the successive elements of the operation of our polymorphic engine, it's time to bring it all together. If it has not reached 0, the loop is repeated. This technique is sometimes used by computer viruses, shellcodes and computer worms to hide their presence. Just like its descriptive name, it holds a continuously changing behavior. An interesting alternative for calculating a delta offset address involves the use of the FPU instruction fnstenv, which stores the environment state of the FPU. In our case we'll stick with 32-bit code. However, there are a number of asymmetric encryption functions, based on public key infrastructure. Reply Delete. Just like regular encrypted viruses, a polymorphic virus infects files with an encrypted copy of itself, which is decoded by a decryption module. Reply. Polymorphic Code is the debut studio album by French one - man band The Algorithm, signed by Basick Records and released on November 19, 2012. The first known polymorphic virus was called 1260, or V2PX, and it was created in 1990 as part of a research project. The use of complex mutation … In this way, it is possible to discover tracing of our code by debuggers including OllyDbg. In 1990, a Polymorphic virus named 1260 / V2PX was created for research purposes. In such cases we cannot refer to parts of the function using absolute memory addresses, because we simply don't know where the function will reside. We will need to determine its address at runtime, through the use of relative addressing. There is a wide variety of encryption algorithms available. These viruses repeatedly change their overt characteristics in an attempt to evade and outwit your computer’s defenses and sabotage your system. They both are capable of changing themselves as they propagate. The prologue of the decryption function is simply the first section of the function, which contains some standard elements like setting up the stack frame and preserving registers. The polymorphic virus is not immune to security. What is a polymorphic virus? Due to the level of complexity of polymorphic engines, and the necessity of an in-depth understanding of assembly language for their creation, these days polymorphic engines are rarely used (one exception to this is Virut which, I'd like to point out, is strongly suspected of being Polish in origin!). Listing 9.Generating the code of the decryption loop. The combination of call and pop r32 can cause the application to be suspected of containing malware. Virus is one type of malware. Heuristic based solutions examine the actions and activities taken by code running on your system and prevent certain things from happening: for example, encrypting files should never happen and many heuristic programs prevent that helping you avoid a ransomware attack. Non-aligned addresses will be read from the slower L2 cache or directly from the computer's RAM. Having generated the entire code of the decryption function, we can now correct any relative addresses used earlier, which in our case is just the address of the encrypted data. using, adding jumps to the code so the instructions are not executed linearly, and, most advanced – multilayer encryption, that is, generated code which in turn contains another layer of decryptor. Before the loop we will initialize the register we have called regSize with the number of blocks which need to be decrypted. This is the main goal of a polymorphic engine, after all! Our decryption function will take just one parameter: a pointer to the output buffer where the decrypted data will go. Subscribe to our newsletter to receive notifications about new articles: Bartosz Wójcik — the creator of software protection systems against cracking, is interested in advanced reverse engineering topics, which he frequently discusses on his computer security blog www.secnews.pl. Replies. Cybercriminals are constantly updating and morphing their virus code. You may have heard of the term "polymorphic virus". Among other things, this contains the memory location of the most recently executed FPU instruction. A polymorphic virus uses a variable encryption key to change each copy of the virus. CyberHoot comes with built in cybersecurity assessments to help our clients do just this. The RSA company even organized a public challenge to break RSA keys, where the largest prize was $US200,000 for cracking a 2048-bit key. Quelques autres codes source de virus. This is due to processor cache effects. Since the public and private keys are mathematically related, it is theoretically possible to “crack” a public key and obtain the private key, however there are no known practical ways of doing this. The epilogue, in other words, the last portion of the function, is where the original value of the EBP register is restored, and if necessary, the sensitive registers ESI EDI EBX, whose state must be preserved across function calls according to the stdcall convention. tools which remove software protection). The code of the polymorphic engine takes about half of the actual virus code, and there are random byte-based blocks inserted between the generated code chains of the decryptor. My grades was in a mess, i was not proud of myself, but something needed to be done you know what i mean. The advantage of these algorithms is that they are heavily studied and their strengths and weaknesses are known. Polymorphic malware isn’t new; the first polymorphic virus dates back to 1989. That is, the code changes itself each time it runs, but the function of the code will not change at all. adding a value to a random register and then taking it away again), generating equivalent instructions (code mutations) in various forms, joined by random comparisons and jumps, generating additional helper functions, e.g. Listing 1.Pseudocode in C++ for the decryption function that we will generate. people who try to break software protection), and to make it harder for automated unpackers to be created (i.e. returning values which were originally put in place by code in the main decryption function, changes to the calling convention used, e.g. Because one polymorphic virus could have hundreds or thousands of variants it makes it more difficult to detect every variant of the virus. The initial exploit of a system often comes from human error, performing an action like downloading and running an infected email attachment, or visiting a website that has been compromised. It's important to remember that the memory where the code is found should be allocated with the correct executable flags. Our polymorphic engine is pretty simple at the moment. However, polymorphic engines have found another use: software protection systems, or exe-protectors, such as PELock, ASProtect, EnigmaProtector, Themida, and Obsidium. After decrypting a data block, the pointers to the encrypted data and the decrypted data buffer are updated, and the loop counter which indicates the number of blocks remaining is decremented. The loop takes successive encrypted blocks of data from the buffer at the end of the function, then carries out all the decryption instructions on each block, and writes the result to the output buffer. Of course, this didn’t stop there. This approach to the delta offset calculation is sometimes used in exploits, e.g. As the name implies, public keys can be safely published on the Internet (like the keys in the PGP encryption system). detect various sequences of computer code known to be used by a given mutation engine to decrypt a virus body. In time, polymorphic algorithms evolved and became ever more sophisticated, in order to make it as difficult as possible for antivirus programs to analyze viruses and run them in an emulated environment. The virus rebuilds itself on the stack with push instructions. In the case of polymorphic viruses, however, this decryption module is also modified on each infection. This article explains all the steps needed to write a C++ program which dynamically generates encryption algorithms in x86 assembly code. To vary their physical file makeup during each infection, polymorphic viruses encrypt their codes and use different encryption keys every time. One of the simplest and best ways to protect your systems from dynamic, changing code is to ensure you have the right type of security solution software in place. Listing 17.Testing the polymorphic engine. This value will be returned in the EAX register. One virus author even created a tool kit called the “Dark Avenger’s Mutation Engine” (also known as MTE or DAME) for other virus writers to use. He also performs software security audits in terms of vulnerability to reverse engineering analysis and protection against cracking. The build routine of the virus is already metamorphic. If memory addresses are correctly aligned, the data can be stored in the fast memory attached to the processor known as L1 cache. Our decryption function will use the standard 32-bit processor registers, and will obtain its one parameter from the stack using the stack frame pointer in the EBP register. 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