Metamorphic malware identification using engine-specific patterns based on co-opcode graphs

A metamorphic virus is a type of malware that modifies its code using a morphing engine. Morphing engines are used to generate a large number of metamorphic malware variants by performing different obfuscation techniques. Since each metamorphic malware has its own unique structure, signature based anti-virus programs are ineffective to detect these metamorphic variants. Therefore, detection of these kind of viruses becomes an increasingly important task. Recently, many researchers have focused on extracting common patterns of metamorphic variants that can be used as micro-signatures to identify the metamorphic malware executables. With the similar motivation, in this work, we propose a novel metamorphic malware identification method, named HLES-MMI (Higher-level Engine Signature based Metamorphic Malware Identification). The proposed method firstly constructs a unique graph structure, called as co-opcode graph, for each metamorphic family, then extracts engine-specific opcode patterns from the graphs. Finally, it generates higher-level signature belonging to each family by representing the extracted opcode-patterns with a binary vector. Experimental results on four datasets produced by different morphing engines demonstrate the effectiveness and efficiency of the proposed method by comparing with several existing malware identification methods.     

Malware classification based on call graph clustering

Each day, anti-virus companies receive tens of thousands samples of potentially harmful executables. Many of the malicious samples are variations of previously encountered malware, created by their authors to evade pattern-based detection. Dealing with these large amounts of data requires robust, automatic detection approaches. This paper studies malware classification based on call graph clustering. By representing malware samples as call graphs, it is possible to abstract certain variations away, enabling the detection of structural similarities between samples. The ability to cluster similar samples together will make more generic detection techniques possible, thereby targeting the commonalities of the samples within a cluster. To compare call graphs mutually, we compute pairwise graph similarity scores via graph matchings which approximately minimize the graph edit distance. Next, to facilitate the discovery of similar malware samples, we employ several clustering algorithms, including k-medoids and Density-Based Spatial Clustering of Applications with Noise (DBSCAN). Clustering experiments are conducted on a collection of real malware samples, and the results are evaluated against manual classifications provided by human malware analysts. Experiments show that it is indeed possible to accurately detect malware families via call graph clustering. We anticipate that in the future, call graphs can be used to analyse the emergence of new malware families, and ultimately to automate implementation of generic detection schemes.     

基于语义的恶意代码行为特征提取及检测方法

提出一种基于语义的恶意代码行为特征提取及检测方法,通过结合指令层的污点传播分析与行为层的语义分析,提取恶意代码的关键行为及行为间的依赖关系;然后,利用抗混淆引擎识别语义无关及语义等价行为,获取具有一定抗干扰能力的恶意代码行为特征.在此基础上,实现特征提取及检测原型系统.通过对多个恶意代码样本的分析和检测,完成了对该系统的实验验证.实验结果表明,基于上述方法提取的特征具有抗干扰能力强等特点,基于此特征的检测对恶意代码具有较好的识别能力.     

Scalable fine-grained behavioral clustering of HTTP-based malware

A large number of today’s botnets leverage the HTTP protocol to communicate with their botmasters or perpetrate malicious activities. In this paper, we present a new scalable system for network-level behavioral clustering of HTTP-based malware that aims to efficiently group newly collected malware samples into malware family clusters. The end goal is to obtain malware clusters that can aid the automatic generation of high quality network signatures, which can in turn be used to detect botnet command-and-control (C&C) and other malware-generated communications at the network perimeter.We achieve scalability in our clustering system by simplifying the multi-step clustering process proposed in [31], and by leveraging incremental clustering algorithms that run efficiently on very large datasets. At the same time, we show that scalability is achieved while retaining a good trade-off between detection rate and false positives for the signatures derived from the obtained malware clusters. We implemented a proof-of-concept version of our new scalable malware clustering system and performed experiments with about 65,000 distinct malware samples. Results from our evaluation confirm the effectiveness of the proposed system and show that, compared to [31], our approach can reduce processing times from several hours to a few minutes, and scales well to large datasets containing tens of thousands of distinct malware samples.     

Determining malicious executable distinguishing attributes and low-complexity detection

Detection of rapidly evolving malware requires classification techniques that can effectively and efficiently detect zero-day attacks. Such detection is based on a robust model of benign behavior and deviations from that model are used to detect malicious behavior. In this paper we propose a low-complexity host-based technique that uses deviations in static file attributes to detect malicious executables. We first develop simple statistical models of static file attributes derived from the empirical data of thousands of benign executables. Deviations among the attribute models of benign and malware executables are then quantified using information-theoretic (Kullback-Leibler-based) divergence measures. This quantification reveals distinguishing attributes that are considerably divergent between benign and malware executables and therefore can be used for detection. We use the benign models of divergent attributes in cross-correlation and log-likelihood frameworks to classify malicious executables. Our results, using over 4,000 malicious file samples, indicate that the proposed detector provides reasonably high detection accuracy, while having significantly lower complexity than existing detectors.     

SBMDS: an interpretable string based malware detection system using SVM ensemble with bagging

Malicious executables are programs designed to infiltrate or damage a computer system without the owner’s consent, which have become a serious threat to the security of computer systems. There is an urgent need for effective techniques to detect polymorphic, metamorphic and previously unseen malicious executables of which detection fails in most of the commercial anti-virus software. In this paper, we develop interpretable string based malware detection system (SBMDS), which is based on interpretable string analysis and uses support vector machine (SVM) ensemble with Bagging to classify the file samples and predict the exact types of the malware. Interpretable strings contain both application programming interface (API) execution calls and important semantic strings reflecting an attacker’s intent and goal. Our SBMDS is carried out with four major steps: (1) first constructing the interpretable strings by developing a feature parser; (2) performing feature selection to select informative strings related to different types of malware; (3) followed by using SVM ensemble with bagging to construct the classifier; (4) and finally conducting the malware detector, which not only can detect whether a program is malicious or not, but also can predict the exact type of the malware. Our case study on the large collection of file samples collected by Kingsoft Anti-virus lab illustrate that: (1) The accuracy and efficiency of our SBMDS outperform several popular anti-virus software; (2) Based on the signatures of interpretable strings, our SBMDS outperforms data mining based detection systems which employ single SVM, Naive Bayes with bagging, Decision Trees with bagging; (3) Compared with the IMDS which utilizes the objective-oriented association (OOA) based classification on API calls, our SBMDS achieves better performance. Our SBMDS system has already been incorporated into the scanning tool of a commercial anti-virus software.     

Architecture of a morphological malware detector

Most of malware detectors are based on syntactic signatures that identify known malicious programs. Up to now this architecture has been sufficiently efficient to overcome most of malware attacks. Nevertheless, the complexity of malicious codes still increase. As a result the time required to reverse engineer malicious programs and to forge new signatures is increasingly longer. This study proposes an efficient construction of a morphological malware detector, that is a detector which associates syntactic and semantic analysis. It aims at facilitating the task of malware analysts providing some abstraction on the signature representation which is based on control flow graphs. We build an efficient signature matching engine over tree automata techniques. Moreover we describe a generic graph rewriting engine in order to deal with classic mutations techniques. Finally, we provide a preliminary evaluation of the strategy detection carrying out experiments on a malware collection.     

Hybrids of support vector machine wrapper and filter based framework for malware detection

Malware replicates itself and produces offspring with the same characteristics but different signatures by using code obfuscation techniques. Current generation Anti-Virus (AV) engines employ a signature-template type detection approach where malware can easily evade existing signatures in the database. This reduces the capability of current AV engines in detecting malware. In this paper we propose a hybrid framework for malware detection by using the hybrids of Support Vector Machines Wrapper, Maximum-Relevance–Minimum-Redundancy Filter heuristics where Application Program Interface (API) call statistics are used as a malware features. The novelty of our hybrid framework is that it injects the filter’s ranking score in the wrapper selection process and combines the properties of both wrapper and filters and API call statistics which can detect malware based on the nature of infectious actions instead of signature. To the best of our knowledge, this kind of hybrid approach has not been explored yet in the literature in the context of feature selection and malware detection. Knowledge about the intrinsic characteristics of malicious activities is determined by the API call statistics which is injected as a filter score into the wrapper’s backward elimination process in order to find the most significant APIs. While using the most significant APIs in the wrapper classification on both obfuscated and benign types malware datasets, the results show that the proposed hybrid framework clearly surpasses the existing models including the independent filters and wrappers using only a very compact set of significant APIs. The performances of the proposed and existing models have further been compared using binary logistic regression. Various goodness of fit comparison criteria such as Chi Square, Akaike’s Information Criterion (AIC) and Receiver Operating Characteristic Curve ROC are deployed to identify the best performing models. Experimental outcomes based on the above criteria also show that the proposed hybrid framework outperforms other existing models of signature types including independent wrapper and filter approaches to identify malware.     

Entropy analysis to classify unknown packing algorithms for malware detection

The proportion of packed malware has been growing rapidly and now comprises more than 80 % of all existing malware. In this paper, we propose a method for classifying the packing algorithms of given unknown packed executables, regardless of whether they are malware or benign programs. First, we scale the entropy values of a given executable and convert the entropy values of a particular location of memory into symbolic representations. Our proposed method uses symbolic aggregate approximation (SAX), which is known to be effective for large data conversions. Second, we classify the distribution of symbols using supervised learning classification methods, i.e., naive Bayes and support vector machines for detecting packing algorithms. The results of our experiments involving a collection of 324 packed benign programs and 326 packed malware programs with 19 packing algorithms demonstrate that our method can identify packing algorithms of given executables with a high accuracy of 95.35 %, a recall of 95.83 %, and a precision of 94.13 %. We propose four similarity measurements for detecting packing algorithms based on SAX representations of the entropy values and an incremental aggregate analysis. Among these four metrics, the fidelity similarity measurement demonstrates the best matching result, i.e., a rate of accuracy ranging from 95.0 to 99.9 %, which is from 2 to 13  higher than that of the other three metrics. Our study confirms that packing algorithms can be identified through an entropy analysis based on a measure of the uncertainty of the running processes and without prior knowledge of the executables.     

Fragmented malware through RFID and its defenses

Malware, in essence, is an infiltration to one’s computer system. Malware is created to wreak havoc once it gets in through weakness in a computer’s barricade. Anti-virus companies and operating system companies are working to patch weakness in systems and to detect infiltrators. However, with the advance of fragmentation, detection might even prove to be more difficult. Malware detection relies on signatures to identify malware of certain shapes. With fragmentation, functionality and size can change depending on how many fragments are used and how the fragments are created. In this paper we present a robust malware detection technique, with emphasis on detecting fragmentation malware attacks in RFID systems that can be extended to detect complex obfuscated and mutated malware. After a particular fragmented malware has been first identified, it can be analyzed to extract the signature, which provides a basis for detecting variants and mutants of similar types of malware in the future. Encouraging experimental results on a limited set of recent malware are presented.     

Malware detection using assembly and API call sequences

One of the major problems concerning information assurance is malicious code. To evade detection, malware has also been encrypted or obfuscated to produce variants that continue to plague properly defended and patched networks with zero day exploits. With malware and malware authors using obfuscation techniques to generate automated polymorphic and metamorphic versions, anti-virus software must always keep up with their samples and create a signature that can recognize the new variants. Creating a signature for each variant in a timely fashion is a problem that anti-virus companies face all the time. In this paper we present detection algorithms that can help the anti-virus community to ensure a variant of a known malware can still be detected without the need of creating a signature; a similarity analysis (based on specific quantitative measures) is performed to produce a matrix of similarity scores that can be utilized to determine the likelihood that a piece of code under inspection contains a particular malware. Two general malware detection methods presented in this paper are: Static Analyzer for Vicious Executables (SAVE) and Malware Examiner using Disassembled Code (MEDiC). MEDiC uses assembly calls for analysis and SAVE uses API calls (Static API call sequence and Static API call set) for analysis. We show where Assembly can be superior to API calls in that it allows a more detailed comparison of executables. API calls, on the other hand, can be superior to Assembly for its speed and its smaller signature. Our two proposed techniques are implemented in SAVE) and MEDiC. We present experimental results that indicate that both of our proposed techniques can provide a better detection performance against obfuscated malware. We also found a few false positives, such as those programs that use network functions (e.g. PuTTY) and encrypted programs (no API calls or assembly functions are found in the source code) when the thresholds are set 50% similarity measure. However, these false positives can be minimized, for example by changing the threshold value to 70% that determines whether a program falls in the malicious category or not.     

Malicious sequential pattern mining for automatic malware detection

Due to its damage to Internet security, malware (e.g., virus, worm, trojan) and its detection has caught the attention of both anti-malware industry and researchers for decades. To protect legitimate users from the attacks, the most significant line of defense against malware is anti-malware software products, which mainly use signature-based method for detection. However, this method fails to recognize new, unseen malicious executables. To solve this problem, in this paper, based on the instruction sequences extracted from the file sample set, we propose an effective sequence mining algorithm to discover malicious sequential patterns, and then All-Nearest-Neighbor (ANN) classifier is constructed for malware detection based on the discovered patterns. The developed data mining framework composed of the proposed sequential pattern mining method and ANN classifier can well characterize the malicious patterns from the collected file sample set to effectively detect newly unseen malware samples. A comprehensive experimental study on a real data collection is performed to evaluate our detection framework. Promising experimental results show that our framework outperforms other alternate data mining based detection methods in identifying new malicious executables.     

多态蠕虫特征码自动提取算法

针对多态技术下变形蠕虫的特征与自动提取算法的问题, 提出一种多态蠕虫特征描述方法, 并给出特征码自动提取算法. 这种结合了PADS和Polygraph优点的MS-PADS特征提取方法, 能在强噪声下快速提取高质量的多态蠕虫特征, 具有低误报率、检测精度高和通用性好等特点.     

基于多级签名匹配算法的Android恶意应用检测*

针对Android恶意应用泛滥的问题,提出了一种基于恶意应用样本库的多级签名匹配算法来进行Android恶意应用的检测。以MD5哈希算法与反编译生成的smali文件为基础,生成API签名、Method签名、Class签名、APK签名。利用生成的签名信息,从每一类恶意应用样本库中提取出这类恶意行为的共有签名,通过匹配待检测应用的Class签名与已知恶意应用样本库的签名,将待测应用中含有与恶意签名的列为可疑应用,并回溯定位其恶意代码,确定其是否含有恶意行为。在测试中成功的发现可疑应用并定位了恶意代码,证明了本系统的有效性。     

Generating regular expression signatures for network traffic classification in trusted network management

Network traffic classification is a critical foundation for trusted network management and security systems. Matching application signatures in traffic payload is widely considered to be the most reliable classifying method. However, deriving accurate and efficient signatures for various applications is not a trivial task, for which current practice is mostly manual thus error-prone and of low efficiency. In this paper, we tackle the problem of automatic signature generation. In particular, we focus on generating regular expression signatures with a certain subset of standard syntax rules, which are of sufficient expressive power and compatible with most practical systems. We propose a novel approach that takes as input a labeled training data set and produces a set of signatures for matching the application classes presented in the data. The approach involves four procedures: pre-processing to extract application session payload, tokenization to find common substrings and incorporate position constraints, multiple sequence alignment to find common subsequences, and signature construction to transform the results into regular expressions. A real life full payload traffic trace is used to evaluate the proposed system, and signatures for a range of applications are automatically derived. The results indicate that the signatures are of high quality, and exhibit low false negatives and false positives.     

Fools Download Where Angels Fear to Tread

Our study illustrates that the risk of getting infected by malware that antivirus protection doesn't detect is alarmingly high. New malware that the antivirus engines don't have signatures for is likely to escape detection by a desktop antivirus solution. Taking precautions while using the Internet can protect users only to a certain extent. If they visit the wrong Web site or download a file infected with 0-day malware, they probably won't be protected from infection. The malware specimens that our antivirus packages didn't detect during our two-week exposure period suggest to us that signature-based antivirus software doesn't provide sufficient protection for users who live on the bleeding edge with respect to where they obtain their software. Coupled with the exponential growth of new malware variants, our findings suggest that antivirus vendors have major problems keeping the signature lag within acceptable limits.     

Linux系统中基于多路径的恶意行为规范挖掘

Linux恶意代码检测是Linux安全框架的一个重要组成部分。大多数现存的依照特征进行检测的方法通常落后于恶意代码的发展,已经不能满足日益迫切的安全需求,而基于行为的检测器往往需要高质量的恶意行为规范。使用了一种基于系统调用的自动挖掘规范技术,并在此基础上开发恶意代码的多执行路径,使其规范更详细更全面,从而提高检测器的检测率。     

Holography: a behavior‐based profiler for malware analysis

Behavior‐based detection and signature‐based detection are two popular approaches to malware (malicious software) analysis. The security industry, such as the sector selling antivirus tools, has been using signature and heuristic‐based technologies for years. However, this approach has been proven to be inefficient in identifying unknown malware strains. On the other hand, the behavior‐based malware detection approach has a greater potential in identifying previously unknown instances of malicious software. The accuracy of this approach relies on techniques to profile and recognize accurate behavior models. Unfortunately, with the increasing complexity of malicious software and limitations of existing automatic tools, the current behavior‐based approach cannot discover many newer forms of malware either. In this paper, we implement ‘holography platform’, a behavior‐based profiler on top of a virtual machine emulator that intercepts the system processes and analyzes the CPU instructions, CPU registers, and memory. The captured information is stored in a relational database, and data mining techniques are used to extract information. We demonstrate the breadth of the ‘holography platform’ by conducting two experiments: a packed binary behavior analysis and a malvertising (malicious advertising) incident tracing. Both tasks are known to be very difficult to do efficiently using existing methods and tools. We demonstrate how the precise behavior information can be easily obtained using the ‘holography platform’ tool. With these two experiments, we show that the ‘holography platform’ can provide security researchers and automatic malware detection systems with an efficient malicious software behavior analysis solution. Copyright © 2011 John Wiley & Sons, Ltd.     

SAS: semantics aware signature generation for polymorphic worm detection

String extraction and matching techniques have been widely used in generating signatures for worm detection, but how to generate effective worm signatures in an adversarial environment still remains a challenging problem. For example, attackers can freely manipulate byte distributions within the attack payloads and thus inject well-crafted noisy packets to contaminate the suspicious flow pool. To address these attacks, we propose SAS, a novel Semantics Aware Statistical algorithm for automatic signature generation. When SAS processes packets in a suspicious flow pool, it uses data flow analysis techniques to remove non-critical bytes. We then apply a hidden Markov model (HMM) to the refined data to generate state-transition-graph-based signatures. To our best knowledge, this is the first work combining semantic analysis with statistical analysis to automatically generate worm signatures. Our experiments show that the proposed technique can accurately detect worms with concise signatures. Moreover, our results indicate that SAS is more robust to the byte distribution changes and noise injection attacks compared to Polygraph and Hamsa.     

Using Entropy Analysis to Find Encrypted and Packed Malware

In statically analyzing large sample collections, packed and encrypted malware pose a significant challenge to automating the identification of malware attributes and functionality. Entropy analysis examines the statistical variation in malware executables, enabling analysts to quickly and efficiently identify packed and encrypted samples.