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An Efficient Approach to Resolve Covert Channels

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An Efficient Approach to Resolve Covert Channels International Journal of Network Security, Vol.20, No.5, PP.898-906, Sept. 2018 (DOI: 10.6633/IJNS.201809 20(5).11) 898 An Efficient Approach to Resolve Covert Channels Muawia A. Elsadig1 and Yahia A. Fadlalla2 (Corresponding author: Muawia A. Elsadig) College of Computer Science and Technology, Sudan University of Science and Technology1 Khartoum, Sudan Lead Consultant/Researcher, InfoSec Consulting, Hamilton, Ontario, Canada2 (Email: [email protected]) (Received May 8, 2017; revised and accepted Oct. 21, 2017) Abstract dition, the database user must obtain security clearance that allows them to access a particular data level [16]. In The competitive edge of many companies and public trust other words, any system must ensure that the users ob- in government institutions can often depend on the secu- tain the data which they are authorized for [35]. There- rity of the information held in their systems. Breaches fore, civilian and military government agencies are used of that security, whether deliberate or accidental, can be to building up their relational database systems based on profoundly damaging. Therefore, security is a highly topi- the hierarchical classification levels such as Top Secret, cal issue for both designers and users of computer systems. Secret, Confidential and Unclassified. A system is said to be secure if it supports the policy of The Mandatory Access Control (MAC) is a common a security model in a demonstrable way. Two users, or security access control model that requires users and re- processes operating on their behalf, are communicating sources to be classified and assigned security labels [14], indirectly or covertly in such a system if they are com- In other words, objects and subject are labelled with dif- municating through means that violate the interpretation ferent security levels [13]. MAC is an approach to restrict of the supported security model. Research to eliminate unauthorized users from accessing objects that hold sen- or resolve covert communication channels is limited com- sitive information. It is a B1 level requirement of the Or- pared to the real, rapid, and often dangerous threats these ange Book [9], and interested readers can see more about channels continuously pose. That is due; at large; to their the Orange Book in [23]. When a system ororganizes ingenious, inventive, and numerous scenarios. In order its data into different classification levels and mandates for any two users to establish a covert channel, they both with its access control utilizing the MAC model, then must know one another's identity. This paper proposes the system will be defined as a Multilevel Secure Sys- a design that is based on the fact that it is impossible tem (MLS). The MLS is an implementation of MAC. It is inside a system for any process to recognize any user, for mainly developed for databases and computers that be- whom other processes are invoked, in order to covertly long to highly sensitive government organizations such as communicate with him or her - identities of all users are the U.S. Department of Defense [10]. In Multilevel Se- hidden. Our design is sought to eliminate covert channels cure Database Management Systems, users are cleared at that are known to a system and those that are unknown different clearance levels (i.e. Top-secret, Secret, Con- and waiting to be discovered and potentially utilized il- fidential and Unclassified. While data is given different licitly. The design is sought to eliminate covert channels sensitivity levels (i.e. Top-secret, Secret, Confidential and indifferent to the scenario they employ. Unclassified) [38]. A covert channel scenario exists if la- Keywords: Covert Channels; Channel bandwidth; Cryp- belled data is being transferred to an unauthorized user tography; Multilevel Security; Network Protocols; Security without violating Mandatory Access Controls. The unau- Model; Security Policy thorized user in this case is a user that hasn't the appro- priate clearance to access this labelled data. Commonly, a covert channel is a method of exploiting a communi- 1 Introduction cation channel by a process in order to pass information without violating the system security policy. It is note- It is well known that a large number of databases contain worthy to mention that any proposal to solve a covert data that needs to be categorized into different security channel problem should take into account the system us- levels to securely manage the access to this data. In ad- ability and usefulness. In other words, a useful covert International Journal of Network Security, Vol.20, No.5, PP.898-906, Sept. 2018 (DOI: 10.6633/IJNS.201809 20(5).11) 899 channel solution is a solution that doesn't diminish the lenge that is posed [6]. Another good contribution in net- usability and performance of the overt channel - a legit- work steganography is done by Wendzel et al. [40]. They imate channel that is supposed to allow labelled data to introduced a unified description that assist in categorizing be accessed by a legitimate user. This paper introduces network hiding methods. This valuable effort provides a a design that is supposed to fully eliminate any potential unified taxonomy of hiding techniques, enables the com- covert channel scenario that is intended to leak labelled parison between them and offers an evaluation framework information to unauthorized parties. to assess hiding methods novelty. The rest of this paper is organized as follows: The It is noteworthy to mention that covert channels are next section gives a general overview of covert channel not always used to threaten information security. Some concepts and their development. Section 3 illustrates the practical uses for covert channels were presented, [11, 12, typical covert channel model, which reflects the general 34, 36] such as use of covert channels by network ad- concept of the covert channel scenario through address- ministrators to distribute secret information among the ing so called prisoners problem. Section 4 sheds some network users, use of covert channels to secure authen- light onto some common fundamental concepts to give a tication processes, etc. As an example of using covert concrete idea that facilitates a full understanding of our channels legitimately, Singh et al. proposed an approach proposed design which is presented in Section 5. Then that uses covert communication to enhance Vehicular Ad- Section 6 outlines the evaluation criteria of the proposed hoc Networks (VANETs) security [34]. VANETs have design. The paper is concluded in Section 7 and subse- become a hot area of research as they pose many se- quently the future work is presented in Section 8. curity challenges [8]. Moreover, any suggested security solution for VANETs has to ensure an acceptable over- head that doesn't affect their protocols performance [7]. 2 Covert Channel Development Singh's model exploits a storage covert channel approach to convey secure data while the transmission of unimpor- A covert channel allows people to exchange hidden infor- tant data can be done through the system overt channel. mation in an undetectable way - in a way that doesn't di- However, this trend, the trend of using covert channels minish legitimate communication procedures, which com- for useful purposes, doesn't change the fact that covert plicates the detection of such kinds of threats. In addition, channels are ongoing, devolved and a dangerous threat, a covert channel can also be exploited to pass malicious as covert channel techniques are developed according to activities such as Trojans and viruses etc. so traditional the rapid development of computer system and network firewall systems couldn't recognize them. protocols. It is illogical to attain full elimination of covert chan- nels; however, it is possible to reduce them through an effi- cient and careful system design. Initially, the covert chan- nel was introduced in stand-alone systems and was later 3 Typical Covert Channel Model extended to exploit computer network environments. Ac- cordingly, there are two scenarios in which covert channels This section introduces the typical concept of covert chan- exist: network-based system covert channels and stand- nels, which is illustrated through the common scenario alone system covert channels. In stand-alone covert chan- that is known as the prisoners problem [33]. nels, two processes of different security levels communi- Alice and Bob are prisoners who wish to communicate cate with each other covertly to leak hidden information, to each other, keeping in mind the end goal is to arrange (i.e. a high security level process leaks secret data to their escape. The possible communication channel that another process with low security level). In, contrast, a can be used to speak to each other is under monitoring network covert channel exploits network protocol to carry by so called Wendy (Warden). Wendy is dedicated to covert messages [4]. watch the communication between them. When Wendy Recently, different techniques have been developed catches any suspicious information, Alice and Bob will be that increasingly magnify covert channel threats. These moved into solitary confinement and that results in killing rapidly developed techniques present security experts any hope for them to exchange any piece of information. with a real challenge to fight against this ongoing threat. Therefore, in order to avoid this situation, Alice and Bob Interested readers are referred to [6], for in depth in- should find a secret channel to exchange their messages in formation on the rapid development of covert channels, a manner such that Wendy cannot be able to detect them. in which a lack of covert channel countermeasures is In this case, this channel is known as a covert channel clearly noticed. In the same context, Elsadig et al. in- which allows two communication parties to exchange their troduced a valuable concept, the network covert chan- secret information covertly without being detected by a nel triangle (DSM - Development, Switching and Micro- monitoring system.
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