Tuesday, September 5, 2017

A Review of Mobile Malware Detection Methods



Abstract—Since the past ten years, smartphones have become widespread. These small devices are growing rapidly with the emergence and popularity of wireless technology. Mobile devices store personal information such as contacts and text messages. While these devices are increasingly preferred in all ages, they are vulnerable to be hurt by malicious codes such as viruses, worms, and so on. As the development of functionality of these devices, the ability to get exploited by malicious activities has also increased. The evolution of mobile malware is thought to have the same direction as PC malware.


I.     INTRODUCTION

Mobile phones have evolved to support multiple functions. As mobile phone functionality improves, the ability to get exploited by malicious activities has also increased. For various services such as social networking and games provided from smartphones with the help of 3rd party applications, these are released to obtain sensitive information from mobile devices. There are many kind of smartphone OSs in the world. The most popular one is Android. Any Third-party vendors can create applications for running on Android devices and put them on the app market such as Play store. In some cases, even a trusted application can share the user's information to others without its consent. The evolution of malware on mobile devices is widely considered to have the same direction as PC malware evolution. Mobile devices incorporate a variety of wireless communication methods, which make it easy to connect, making it a simple target for malware. Like Computers (PC), the mobile devices can access the Internet for web browsing and emails. It also has a function to communicate with WLAN, SMS/MMS, Bluetooth connection. It’s most important and interesting reason to believe that attackers use mobile devices since its way more popular among the users. However, with the help of technology and detection algorithms for development, special attention is needed to protect these network devices from malware.

II.     Research Objectives

Due to the expansion of mobile devices in the world, the no of malware attacking mobile devices is also increasing. special attention is needed to protect these devices from malware. There are many types of threats on mobile devices. Some of them will be described in the section III. In addition to that, the history of mobile threats will be discussed. Many researchers have done various kind of researches regarding to that particular topic. In the section IV, a review of that publications will be discussed.

III.     Definitions and Categories

A.     Types of Attacks

The work by Dagon et al. [1] has been examined the attacks types. These attacks types have been listed below.

                                                                                Table 1: Types of Mobile Attacks
Security Goals
Attacks Types
Confidentiality
Theft of data, blue-bugging, blue-snarfing
Integrity
Mobile-hijacking
Availability
Denial-of-service and battery draining

1)     Theft of data

It is an act of stealing information stored on a computer, server, or other device from an unknown victim, infringing privacy or obtaining confidential information. Attackers always try to obtain dynamic and static information. Dynamic information contains location data, power usage, and other sensitive data, that the device does not usually capture [1]. Static information contains data that mobile devices store or send over the network. The blue-snarfing and blue-bugging attacks are examples of theft of data. The blue-bugging attack gives unauthorized access to the mobile phone and spies phone calls. However, this attack has moved along to being able to control/move around/mislead the different functions of the phone [1]. Blue-snarfing attack is unauthorized access and data retrieval from applications.



2)     Denial-of-Service (DoS)

DoS can be done by flooding unusual traffic to the device. And also it can be done by draining the power or performance of the mobile devices. Now, it is very easy to crash most Bluetooth applications on mobile devices by sending useful packets, corrupted packets and wrong file formats repeat. DoS is a major attack type that can be exploited known vulnerabilities [2].

3)     Mobile-hijacking

Some harmful programs or apps tries to use the victim's mobile resources. Pilfered duplicates of PC recreations were contaminated with infections that sent costly SMS messages when clients played unlawful duplicates. Hijacking phone resources are not unexpected.

B.     Threats on Mobile Devices

These are malicious software targeting mobile phones and wireless compatible PDA, causing system collapse and loss or leakage of confidential information by means of WLAN Bluetooth, SMS/MMS. There are various assault vectors, undermining the security of cell phones. There are three main types of attacks: malware attacks, grayware attacks, spyware attacks.

1)     Malware

This type of attack steals the sensitive information of mobile devices. And also these attacks can damage the devices [22]. If the device is vulnerable and tricks the user to install unwanted applications that the attacker can get the device root access. There are many types of malware. Several attacks are shown below.

a)                   SMS attacks

In SMS attacks, an attacker can advertise and disseminate phishing links. An attacker can also exploit vulnerabilities by using SMS messages [22].

b)                   Bluetooth attacks

In Bluetooth attacks, an attacker can steal victim sensitive data from the device, and track the mobile location. With Blue-bugging, an attacker can launch software containing malicious activity and listen to conversations [22].

c)                    Phone jail-breaking

With jail-breaking, an attacker can remove the effect on the security of the operating system and it allows to install applications without additional signatures on the OS. It attracts users to take advantage of additional features [22].

d)                   Premium rate attacks

The premium rate service can deliver valuable useful content to the mobile devices. Users can receive information about financial, technical support, or adult services When used in a legitimate way [22].

2)     Spyware

Spyware is another type of attack that is installed on a computer or mobile devices without knowledge of the owner and collects the owner's personal information. By installing applications without user permissions, spywares can access the device physically. By collecting information about the victim's phone, it is sent to the attacker.

3)     Grayware

Graywares are applications that act in a way that is irritating or undesirable. Most probably, grayware collects the data from mobile devices for marketing purposes. Their goal is not to hurt clients but rather to trouble them.

C.     Attacks on Mobile Devices

Looking at the history of attacks, many Trojan horses, worms and viruses have entered the mobile world and are being influenced. Well known examples for some threats on Symbian-based smart phones include Cabir, Skull and Mabir [1]. Many of these variants viruses strengthen the attack and reveal unexpected and unexpected levels of exposure. According to McAfee 2008, mobile security report, almost 14% of worldwide versatile clients had been specifically tainted or had known somebody who was contaminated by a portable infection. The one of the key characteristics that differentiate threat actors is Motivation. Despite the fact that not each actor needs to take information amid each battle to fulfill a goal, many crusades require it. Figure 1 below describes the motivations of threat actors [3].


State-based entities generally try to gain strategic advantage, but it often targets intellectual property rights. The financial goal of an organized criminal makes it easy to understand its motivation. It tends to focus on large credit cards, banking transactions, or personally identifiable information.
Hacktivists are probably the hardest to stop, as internal data can affect the reputation of the organization.

                                                                                                              

Most of, Much of security breaches in past years have been easily detectable. They were complex with arranging, focusing on, stalking and running. According to the McAfee et al. [3], a change during the past two years, with a significant increase in the number of technically sophisticated attacks has been identified. It looks like fragmentary invasion, but it is hiding in inactive code, waiting for an unprotected moment. These threats avoid signature-based ancestor traps, changes by new deployment using encryption and dynamic code changes, and prevent data corruption.
Since the popularity of Android OS, the possibility of being vulnerable is at higher level. The malware called Slocker rose to become a more prominent threat in 2015 [4]. Slocker's growing popularity indicates that mobile malware targets content stored on the device.



If one malicious program shares another code or behavioral feature, it is usually considered to belong to the same family.
Individual threats of malware families are often detected by security software and identify the essential characteristics of families. Figure 3 describes top ten android malwares in 2015 and the things that they are going to do according to the F-Secure Threat Report 2015.


D. Approaches in Malware Detection
  
Malware needs to be analyzed to understand the risks associated with malwares. In order to clarify the behavior and function of malware, many detection methods exist in the literature. In recent years, interest in malware detection technology of mobile devices has increased. Three main approaches were considered.

1)     Static analysis

Static analysis inspects software properties and source code to investigate downloaded app. However, software encryption technology makes static analysis difficult. Static analysis is further divided into two categories.

a)                   Signature-based detection

Signature-based detection uses specific patterns such as byte sequences or known malicious instruction sequences to detect attacks. In this detection method, the detected patterns are referred as signatures [5]. Signature detection can identify malicious activities before infecting.

b)                  behavior-based detection

This is another general technique that looks for abnormal behavior based on the operation checker resident in memory. In this matter, the user is alerted. Behavior checkers have the disadvantage that some changes have been made to the system before malicious activity is detected.

2)     Dynamic analysis

Dynamic analysis runs the application in a different environment and tracks its execution behavior. Dynamic analysis can be used to reveal the natural behavior of malware when the executed code is analyzed. Therefore, it is not affected by obfuscation attempt.

3)     Integrity Checking

Integrity checking uses a log of all files existing in the system. The log contains information of files such as file size, timestamp, checksum, etc. Each time the integrity checker runs, the files on the system are checked and compared with previously saved characteristics.

IV.     Review Of The Literature

Some relevant related work that includes the above-mentioned malware detection techniques will be presented and reviewed.

D.Venugopal et al. [5], has described a method of representing signatures for detecting viruses in mobile devices. In this, the hash table is used to store hash values of virus signature for fast matching. The first matching signature cut was used to speed up that process. This represents a part that is unlikely to occur in a regular file before matching the whole signature. Nokia 6682 device running on Symbian OS was used to test this method. As a result, this method was 98% faster than the sequential scan. Using this method, new malware which completely different from the previous malware cannot be detected. To improve the detection, this method needs to be combined with more sophisticated malware detection methods such as heuristic scanning and detection. As the virus evolved, the technology to protect the virus had to evolve. The detection of malicious code in this context includes more sophisticated approaches such as heuristics and behavior analyzers [6].

D. Venugopal, G. Hu, and N. Roman et al. [7], have described a method that is different to the previous. In there an intelligent heuristic method is used to detect viruses in the mobile devices. It uses Dynamic Link Libraries (DLLs) to detection. The virus uses the list of DLL functions to indicate the nature of the virus on that function. With this approach, new viruses can be detected. According to the research, Symbian-OS is used to test this method, and for non-virus programs, it has got 95% detection rate and 0 false detection rate for all viruses.

F. Peters, A. Shmidt, S.Albayrak and F.Lamour et al. [8], describe a machine learning algorithm for detecting malicious activity of mobile devices such as smartphones. A remote anomaly detection system performs anomaly detection. Each smartphone behaves as a client and sends a series of functions pulled out by studying different resources measurements, hardware and software to the remote anomaly detection system. These functions are stored in the database. The detection components access the database to analyze malicious activity data. Using Symbian-OS and Windows Mobile, this method has been tested. As a result, there are disk space savings, computational and communication cost savings, and positive impact on battery life.

Kim at el. [9] has shown a Proposal of a framework for detecting and monitoring threats of energy greed by constructing power usage from gathered instances. After generating the power signatures, the signatures available in the database is compared by the data analyzer. Batyuk et al. [10] proposed a system for static analysis of android applications. Next, the method is developed by overcoming the security threat introduced by the application and disabling malicious functionality. Ontang et al. [11] proposed a secure application interaction framework. It works by increasing the architecture of android security for protection of interfaces and raising interaction policies.

J. Cheng et al. [12] presented a behavior checking system for smart phone called SmartSiren that consists of cooperative virus detection and alert system. On each smartphone, there is a system that running a light-weight agent. The agent tracks communication activity on the device and periodically reports the summary of these activities to the proxy. A centralized proxy is used to assist the virus detection and alert processes. The proxy collaboratively analyzes the reports received and identifies single-device or system-wide virus manner. When a potential virus is detected, the proxy sends an alert to both the infected device and a subset of the infected device (which may be in direct contact with the infected device). As a result, SmartSiren prevents wide area virus outbreaks. A better result can be obtained by using this method instead of using signature based detection.


Bose et al. [13] presented a behavioral detection framework. It works in a way of representing the malware behavior. It discovers applications actions logical order to do that. Malicious behavior is distinguished from normal behavior by training the SVM. The system is evaluated with an accuracy of 96% for both real world and pseudo mobile malware.

The method called pBMDS based on behavior-based malware detection has been described by L. Xie et al. [14]. It uses an approach that is probabilistic by matching user inputs with system calls to detect distrustful activities in mobile phones. It observes the specific behavior of mobile phone applications and operations users on input and output constrained devices. Hidden markov model(HMM) is leveraged to learn user-behavior and malware behavior for discrimination of differences between them. As a result, pBMDS was shown to be effective, lightweight, easy to deploy, and capable of detecting unknown malware.

Wei et al. [15] proposed a static feature-based approach and developed a system called Droid Mat that can detect and distinguish android malwares. Their mechanisms consider the static information characterizing android malware about access permissions, intents, and components, and apply a clustering algorithm to enhance malware modeling capabilities. Finally, DroidMat is efficient as it can predict 1738 applications in half the time compared to Androguard, a well-known tool published in Blackhat 2011.

Enck et al. [16], proposed Apps-playground framework for automatic dynamic analysis of android applications. This allows to analyze malicious applications as well as applications that leak personal data from smartphones without user consent. For dynamic analysis, a detection technique including a function of searching application code as much as possible is necessary, and the environment must be realistic to the extent that a malicious application cannot be obfuscated. Automated analysis code effectively explores applications by integrating discovery. Detection technology detects malicious functionality while running applications. It includes suspicious traces that monitor TaintDroid’s confidential information APIs, such as the SMS API, and perform kernel-level monitoring for tracing of root exploits. Automatic exploration techniques are useful for code coverage of applications by simulating events. For automatic discovery of android applications, intelligent black box execution tests and Fuzzy tests are used. Disguise technology creates a realistic environment by providing data such as IMEI, contacts, SMS, GPS coordinates etc.

An Android application sandbox (AA sandbox) system was proposed by T. Blasing et al. [17] for analysis of android application consists of high speed static pre-check function and kernel space sandbox. Static analysis and dynamic analysis are used to perform distrustful application detection in the android application. AA Sandbox takes APK file and find out following files by decompressing them-Androidmanifest.xml, res/, classes.dex.
Security permissions and application descriptions are contained in the manifest file. The Res/ folder defines the layout, the graphical user interface (GUI) element and the language of the application. The Classes.dex file includes runnable program code to run on the dalvik VM. This code is compiled into a Java file using baksmali and it searches for suspicious code patterns. Monkey program is created for application stress testing. These monkey programs generate a pseudo-random sequence of user events. This is used for hijacking logging operation system calls and is useful for obtaining application logging behavior at the system level. For testing purposes, approximately 150 applications are gathered [17].

A dynamic analysis system supported runtime behavior for android applications has been presented by L. X. Min and Q. H. Cao et al. [18]. That system includes event detector, log monitor and parser. Event triggers can use static analysis to simulate user behavior. The static analyzer gets the support of the application .apk file and generates manifest.xml and java code. Semantic analysis retrieves a list of risk-based permissions, activities, and services, including other information such as hash codes and package names. A control flow graph (CFG) about an application is generated by dataflow analysis [18]. It uses a way of mapping user-defined methods and API calls to do that. Confidential information on applications can be obtained by executing applications with customized emulators using loadable LKM. In the log recorded by the debug tool logcat, highly confidential operation is sent to the log parser. The log monitor analyzes the log data by collecting log data while the application is running. The parser analyzes the log data by extracting confidential information and filtering unnecessary information. 82 of 350 apps that were got from Amazon Android market showed that they leak the user’s private sensitive data [18].

The authors mentioned a method called Paranoid Android [19]. It uses remote security servers which has exact copy of the mobile phones in virtual environment.  It is for checking the security of smart phones. Because the server is not subject to the same constraints as smart phones, multiple detection methods can be applied simultaneously. The execution of the phone is recorded and played on the security server in the cloud. Paranoid Android uses a warning mechanism to warn the user about the malicious activity that is going to be happen, when an attack is detected. If the device is already sieged by the attack, it can be returned to. Using an Android mobile phone, the prototype of Paranoid Android was tested [19]. As a result, even during the high activity period, the transmission overhead is maintained at 2.5 Kbps or less, the idle period is shortened, and the battery life is shortened by about 30%.

A framework for a background monitoring system is described by M. Becher and F.C. Freiling et al. [20]. It works by collecting the software to be installed by the user on the device and automatically perform a dynamic analysis of the software. The analysis system uses mobile networks as analysis locations rather than mobile devices for two reasons. First, mobile networks have more computing power to carry out more thorough analysis. Second, since it is easier to handle compared to handling local connections, it is pretended that mobile network will deliver the most software. Therefore, suspicious manner in the mobile network is analyzed by software before the user installs the software on the mobile device. The automatic dynamic analysis where system calls are recorded and malicious acts are analyzed helps to do that. There are three stages that dynamic analysis is done. In the first stage, the software components are collected. In the second stage, we collected samples are analyzed with specific modules called mobile sandboxes. This method is similar to the process described by T. Blasing [17]. This module runs the sample in an environment where steps of the examined sample can be watched. This will result in a series of API calls used during program execution. The third step is providing a response to the analysis. When malicious activity is detected the installation of the software can be rejected by mobile network operators. It also might send a message to alert the user that the program violates the user’s or network’s security profile.

In additions to these methods, an architecture for automatic downloading of android applications from the android market has been proposed by R. Johnson, Z. Wang, C. Gagnon et al. [21]. Various algorithms used to search applications, such as downloading applications by application category. With static analysis, required permissions can be obtained based on its functionality. The authorization name is searched in the Android source code and mapped in the API call to see if the requested access right is correct. The program examines all the files of the application and gets a list of method calls used by the application. Each method call is then compared with the method calls listed in the permission protected Android API call to find the exact permissions. The similarities and differences are identified in the restricted permission set by comparing them with all the permissions nominated in the AndroidManifest.xml file [21], no additional permissions, no access rights, and no permission set required for the function.

V. FUTURE RESEARCH

The threat associated with mobile malware is expanding due to the expansion of mobile devices all over the world. New malicious mobile programs are introduced daily with the incrementing of the mobile technologies. Mobile devices are the majority of our daily lives, Connecting us to social media, banking, videos, gaming, online shopping etc. Therefore, preventing of those mobile threats are highly recommended. In the review, the history and the current state of mobile malware detection techniques have been discussed. The future of mobile malware and detection techniques should be talked to make the future better.
In the review, it was shown that anomaly detection is mainly performed by a proxy that is off from the attack source. This type of detection concept has two main advantages. First, a large processing speed and power usage are required by the large-scale detection solutions. Second, as the reactive approach is always better than being aggressive, the proxy can inform other users of potential attacks before the entire network is involved in malware activity. Because reactive approach is always better than proactive. Based on the outline of a quickly changing attack, there is no way to specify one method for the future of virus detection. The thing that is required is an efficient malicious activity detection method. The spread rate can be reduced by it and also could be applied at network level to protect the spreading through network routes. It seems that there is a high possibility that the malicious code detection technology that will appear in the future will be essentially distributed. It is thought that focus will shift from endpoint protection to network-wide protection. There are several recommendations for designing algorithms to detect mobile-based applications including malware. These are:
To build a feature set that detects mobile malware, multiple feature extraction sources are needed.
In order for developers to recognize vulnerabilities related to mobile malware, domestic and foreign databases are required to report malware incidents.
Machine communication and authentication tools must be used across multiple device platforms.
To improve the detection rate, an artificial intelligence algorithm should be used.
This review forms the foundation for future work on mobile malware detection. It has also established the framework of investigation necessary to advance towards the development of the network-wide protection framework.

VI.     Conclusion

Smartphones are becoming increasingly popular in positions of power, sensors and communication. Modern smartphones offer many services such as messaging, Internet browsing, e-mail transmission, games etc. in addition to traditional voice services. Because of its multifunctionality, new security threats are emerging in mobile devices. This paper is a review of malware detection techniques for mobile devices. Additionally, the history and current situation of mobile threats and vulnerabilities have been discussed in this paper. Problems related to traditional signature-based detection methods are also highlighted. Various mobile malware detection methods were described. This paper provides sufficient literature for the researchers on the mobile malware detection methods and hope that it will motivate the researchers and practitioners to examine mobile security issues and its applications.

Acknowledgment

This work very well supported in part of all the authors who has shared their knowledge along with their researches mentioned in the below. And we thank our supervisor who in charge of this module Mr.Amila Nuwan Senarathne who guided us throughout the semester.

References

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[21]  R. Johnson, Z. Wang, C. Gagnon and A. Stavrou, “Analysis of Android Applications' Permissions,” 2012 IEEE Sixth International Conference on Software Security and Reliability Companion, Gaithersburg, MD, 2012, pp. 45-46.
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A.A.C.S Wickramasinghe, Undergraduate, SLIIT 
G.A.A.I.S De Silva, Undergraduate, SLIIT





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