The ecosystem of open source software (OSS) has been growing considerably in size. In addition, code clones - code fragments that are copied and pasted within or between software systems - are also proliferating. Although code cloning may expedite the process of software development, it often critically affects the security of software because vulnerabilities and bugs can easily be propagated through code clones. These vulnerable code clones are increasing in conjunction with the growth of OSS, potentially contaminating many systems. Although researchers have attempted to detect code clones for decades, most of these attempts fail to scale to the size of the ever-growing OSS code base. The lack of scalability prevents software developers from readily managing code clones and associated vulnerabilities. Moreover, most existing clone detection techniques focus overly on merely detecting clones and this impairs their ability to accurately find "vulnerable" clones.
In this paper, we propose VUDDY, an approach for the scalable detection of vulnerable code clones, which is capable of detecting security vulnerabilities in large software programs efficiently and accurately. Its extreme scalability is achieved by leveraging function-level granularity and a length-filtering technique that reduces the number of signature comparisons. This efficient design enables VUDDY to preprocess a billion lines of code in 14 hour and 17 minutes, after which it requires a few seconds to identify code clones. In addition, we designed a security-aware abstraction technique that renders VUDDY resilient to common modifications in cloned code, while preserving the vulnerable conditions even after the abstraction is applied. This extends the scope of VUDDY to identifying variants of known vulnerabilities, with high accuracy. In this study, we describe its principles and evaluate its efficacy and effectiveness by comparing it with existing mechanisms and presenting the vulnerabilities it detected. VUDDY outperformed four state-of-the-art code clone detection techniques in terms of both scalability and accuracy, and proved its effectiveness by detecting zero-day vulnerabilities in widely used software systems, such as Apache HTTPD and Ubuntu OS Distribution.
Internet protocol (IP) spoofing is a serious problem on the Internet. It is an attractive technique for adversaries who wish to amplify their network attacks and retain anonymity. Many approaches have been proposed to prevent IP spoofing attacks; however, they do not address a significant deployment issue, i.e., filtering inefficiency caused by a lack of deployment incentives for adopters. To defeat attacks effectively, one mechanism must be widely deployed on the network; however, the majority of the antispoofing mechanisms are unsuitable to solve the deployment issue by themselves. Each mechanism can work separately; however, their defensive power is considerably weak when insuffi- ciently deployed. If we coordinate partially deployed mechanisms such that they work together, they demonstrate considerably superior performance by creating a synergy effect that overcomes their limited deployment. Therefore, we propose a universal antispoofing (UAS) mechanism that incorporates existing mechanisms to thwart IP spoofing attacks. In the proposed mechanism, intermediate routers utilize any existing anti-spoofing mechanism that can ascertain if a packet is spoofed and records this decision in the packet header. The edge routers of a victim network can estimate the forgery of a packet based on this information sent by the upstream routers. The results of experiments conducted with real Internet topologies indicate that UAS reduces false alarms up to 84.5% compared to the case where each mechanism operates individually.
Domain Name System (DNS) traffic has become a rich source of
information from a security perspective. However, the volume of
DNS traffic has been skyrocketing, such that security analyzers
experience difficulties in collecting, retrieving, and
analyzing the DNS traffic in response to modern Internet
threats. More precisely, much of the research relating to DNS
has been negatively affected by the dramatic increase in the
number of queries and domains. This phenomenon has necessitated
a scalable approach, which is not dependent on the volume of
DNS traffic. In this paper, we introduce a fast and scalable
approach, called PsyBoG, for detecting malicious behavior
within large volumes of DNS traffic. PsyBoG leverages a signal
processing technique, power spectral density (PSD) analysis, to
discover the major frequencies resulting from the periodic DNS
queries of botnets. The PSD analysis allows us to detect
sophisticated botnets regardless of their evasive techniques,
sporadic behavior, and even normal users’ traffic.
Furthermore, our method allows us to deal with large-scale DNS
data by only utilizing the timing information of query
generation regardless of the number of queries and domains.
Finally, PsyBoG discovers groups of hosts which show similar
patterns of malicious behavior. PsyBoG was evaluated by
conducting experiments with two different data sets, namely DNS
traces generated by real malware in controlled environments and
a large number of real-world DNS traces collected from a
recursive DNS server, an authoritative DNS server, and Top-
Level Domain (TLD) servers. We utilized the malware traces as
the ground truth, and, as a result, PsyBoG performed with a
detection accuracy of 95%. By using a large number of DNS
traces, we were able to demonstrate the scalability and
effectiveness of PsyBoG in terms of practical usage. Finally,
PsyBoG detected 23 unknown and 26 known botnet groups with 0.1%
Prevalent Wi-Fi networks have adopted various protections to prevent eavesdropping caused by the intrinsic shared nature of wireless medium. However, many of them are based on pre-shared secret incurring key management costs, and are still vulnerable from practical countermeasures. In this study, we investigate the feasibility of using defensive jamming technique to protect enterprise Wi-Fi networks from potential eavesdroppers. This non-cryptographic approach requires neither any pre-shared key or high deployment costs. Defensive jammers geographically confine the wireless coverage of Wi-Fi access point, and thus block the message reception outside an arbitrary boundary at a physical layer. We provide a theoretical model fine tuning the jamming parameters for jammer placement. We then discuss practical considerations including optimized jammer arrangement algorithms, interference countermeasures to legitimate communications, and countermeasures against advanced attackers.
Software vulnerability has long been considered an important threat to the system safety. A vulnerability is often reproduced because of the frequent code reuse by programmers. Security patches are usually not propagated to all code clones; however, they could be leveraged to discover unknown vulnerabilities. Static code auditing approaches are frequently proposed to scan source codes for security flaws; unfortunately, these approaches generate too many false positives. While dynamic execution analysis methods can precisely report vulnerabilities, they are ineffective in path exploration, which limits them to scale to large programs. With the purpose of detecting vulnerability in a scalable way with more preciseness, in this paper, we propose a novel mechanism, called software vulnerability discovery using Code Clone Verification (CLORIFI), that scalably discovers vulnerabilities in real world programs using code clone verification. In the beginning, we use a fast and scalable syntax-based way to find code clones in program source codes based on released security patches. Subsequently, code clones are being verified using concolic testing to dramatically decrease the false positives. In addition, we mitigate the path explosion problem by backward sensitive data tracing in concolic execution. Experiments have been conducted with real-world open-source projects (recent Linux OS distributions and program packages). As a result, we found 7 real vulnerabilities out of 63 code clones from Ubuntu 14.04 LTS (Canonical, London, UK) and 10 vulnerabilities out of 40 code clones from CentOS 7.0 (The CentOS Project(community contributed)). Furthermore, we confirmed more code clone vulnerabilities in various versions of programs including Rsyslog (Open Source(Original author: Rainer Gerhards)), Apache (Apache Software Foundation, Forest Hill, Maryland, USA) and Firefox (Mozilla Corporation, Mountain View, California, USA). In order to evaluate the effectiveness of vulnerability verification in a systematic way, we also utilized Juliet Test Suite as measurement objects. The results show that CLORIFI achieves 98% accuracy with 0 false positives.
Internet attacks often use IP spoofing to forge the source IP address of packets, and thereby hide the identity of the source. It causes many serious security problems such as the difficulty of packet authenticity and IP traceback. While many IP spoofing prevention techniques have been proposed apart from ingress filtering, none have achieved widespread real-world use. One main reason is the lack of properties favoring incremental deployment, an essential component for new technology adoption. An incrementally deployable protocol should have three properties: initial benefits for early adopters, incremental benefits for subsequent adopters, and effectiveness under partial deployment. Since no previous anti-spoofing solution satisfies all three properties, we propose an anti-spoofing mechanism called “BGP-based Anti-Spoofing Extension” (BASE). BASE is an anti-spoofing protocol designed to fulfill the incremental deployment properties. Furthermore, BASE is designed to work in the software-defined networks (SDN). It gives a motivation to network operators to adopt BASE into their network, since the idea of SDN supports the large scale network control with a simple operation. Based on simulations using a model of Internet connectivity, BASE shows desirable IP spoofing prevention capabilities under partial deployment. We find that just 30% deployment can drop about 97% of attack packets. It is shown that BASE not only provides benefits to early adopters, but also outperforms previous anti-spoofing mechanisms.
The sharp increase in smartphone malware has become one of the most serious security problems. Since the Android platform has taken the dominant position in smartphone popularity, the number of Android malware has grown correspondingly and represents critical threat to the smartphone users. This rise in malware is primarily attributable to the occurrence of variants of existing malware. A set of variants stem from one malware can be considered as one malware family, and malware families cover more than half of the Android malware population. A conventional technique for defeating malware is the use of signature matching which is efficient from a time perspective but not very practical because of its lack of robustness against the malware variants. As a counter approach for handling the issue of variants behavior analysis techniques have been proposed but require extensive time and resources. In this paper, we propose an Android malware detection mechanism that uses automated family signature extraction and family signature matching. Key concept of the mechanism is to extract a set of family representative binary patterns from evaluated family members as a signature and to classify each set of variants into a malware family via an estimation of similarity to the signatures. The proposed family signature and detection mechanism offers more flexible variant detection than does the legacy signature matching, which is strictly dependent on the presence of a specific string. Furthermore, compared with the previous behavior analysis techniques considering family detection, the proposed family signature has higher detection accuracy without the need for the significant overhead of data and control flow analysis. Using the proposed signature, we can detect new variants of known malware efficiently and accurately by static matching. We evaluated our mechanism with 5846 real world Android malware samples belonging to 48 families collected in April 2014 at an anti-virus company; experimental results showed that; our mechanism achieved greater than 97% accuracy in detection of variants. We also demonstrated that the mechanism has a linear time complexity with the number of target applications.
The number of malicious applications, sometimes
known as malapps, in Android smartphones has increased
significantly in recent years. Malapp writers abuse repackaging
techniques to rebuild applications with code changes.
Existing anti-malware applications do not successfully defeat
or defend against the repackaged malapps due to numerous
variants. Software-based attestation approaches widely used in a
resource-constrained environment have been developed to detect
code changes of software with low resource consumption. In this
paper, we propose a novel software-based attestation approach,
called MysteryChecker, leveraging an unpredictable attestation
algorithm. For its unpredictable attestation, MysteryChecker
applies the concept of code obfuscation, which changes the syntax
in order to avoid code analysis by adversaries. More precisely,
unpredictable attestation is achieved by chaining randomly selected
crypto functions. A verifier sends a randomly generated
attestation module, and the target application must reply with
a correct response using the attestation module. Also, the target
application periodically receives a new module that contains a
different attestation algorithm. Thus, even if the attacker analyzes
the attestation module, the target application replaces the existing
attestation module with a new one and the analysis done by
the attacker becomes invalid. Experimental results show that
MysteryChecker is completely able to detect known and unknown
variants of repackaged malapps, while existing anti-malware
applications only partially detect the variants.
The botnets are one of the most dangerous species of network-based attack. They cause severe network disruptions through massive coordinated attacks nowadays and the results of this disruption frequently cost enterprises large sums in financial losses. In this paper, we make an in-depth investigation on the issue of botnet detection and present a new security visualization tool for visualizing botnet behaviors on DNS traffic. The core mechanism is developed with the objective of enabling users to recognize security threats promptly and mitigate the damages by only visualizing DNS traffic in cylindrical coordinates. We compare our visualization method with existing ones and the experimental results show that ours has greater perceptual efficiency. The ideas and results of this study will contribute toward designing an advanced visualization technique that offers better security. Also, the approach proposed in this study can be utilized to derive new and valuable insights in security aspects from the complex correlations of Big Data.
Malicious activities on the Internet are one of the most dangerous threats to Internet users and
organizations. Malicious software controlled remotely is addressed as one of the most critical methods
for executing the malicious activities. Since blocking domain names for command and control (C&C) of
the malwares by analyzing their Domain Name System (DNS) activities has been the most effective
and practical countermeasure, attackers attempt to hide their malwares by adopting several evasion
techniques, such as client sub-grouping and domain flux on DNS activities. A common feature of the
recently developed evasion techniques is the utilization of multiple domain names for render malware
DNS activities temporally and spatially more complex. In contrast to analyzing the DNS activities for a
single domain name, detecting the malicious DNS activities for multiple domain names is not a simple
task. The DNS activities of malware that uses multiple domain names, termed multi-domain malware,
are sparser and less synchronized with respect to space and time.
In this paper, we introduce a malware activity detection mechanism, GMAD: Graph-based Malware
Activity Detection that utilizes a sequence of DNS queries in order to achieve robustness against evasion
techniques. GMAD uses a graph termed Domain Name Travel Graph which expresses DNS query sequences
to detect infected clients and malicious domain names. In addition to detecting malware C&C domain
names, GMAD detects malicious DNS activities such as blacklist checking and fake DNS querying. To
detect malicious domain names utilized to malware activities, GMAD applies domain name clustering
using the graph structure and determines malicious clusters by referring to public blacklists. Through
experiments with four sets of DNS traffic captured in two ISP networks in the U.S. and South Korea,
we show that GMAD detected thousands of malicious domain names that had neither been blacklisted
nor detected through group activity of DNS clients. In a detection accuracy evaluation, GMAD showed
an accuracy rate higher than 99% on average, with a higher than 90% precision and lower than 0:5% false
positive rate. It is shown that the proposed method is effective for detecting multi-domain malware
activities irrespective of evasion techniques.
Distributed denial-of-service (DDoS) attacks are considered to be among the most crucial security challenges in current networks because they significantly disrupt the availability of a service by consuming extreme amount of resource and/or by creating link congestions. One type of countermeasure against DDoS attacks is a filter-based approach where filter- based intermediate routers within the network coordinate with each other to filter undesired flows. The key to success for this approach is effective filter propagation and management techniques. However, existing filter-based approaches do not consider effective filter propagation and management. In this paper, we define three necessary properties for a viable DDoS solution: how to practically propagate filters, how to place filters to effective filter routers, and how to manage filters to maximize the efficacy of the defense. We propose a novel mechanism, called Adaptive Probabilistic Filter Scheduling (APFS), that effectively defends against DDoS attacks and also satisfies the three necessary properties. In APFS, a filter router adaptively calculates its own marking probability based on three factors: 1) hop count from a sender, 2) the filter router’s resource availability, and 3) the filter router’s link degree. That is, a filter router that is closer to attackers, has more available resources, or has more connections to neighbors inserts its marking with a higher probability. These three factors lead a victim to receive more markings from more effective filter routers, and thus, filters are quickly distributed to effective filter routers. Moreover, each filter router manages multiple filters using a filter scheduling policy that allows it to selectively keep the most effective filters depending on attack situations. Experimental results show that APFS has a faster filter propagation and a higher attack blocking ratio than existing approaches that use fixed marking probability. In addition, APFS has a 44% higher defense effectiveness than existing filter-based approaches that do not use a filter scheduling policy.
DDoS attacks continue to be a major threat to
network security. Several new types of attacks such as Layer-
7 attacks (e.g., HTTP flood, Slowloris, RUDY, etc.) have
emerged. We propose a novel DDoS defense mechanism
called DROP-FAST. Our mechanism provides distributed
DDoS defense utilizing multiple replicas of the protected
server throughout a cloud infrastructure. DROP-FAST is
dynamic and can adapt by controlling the number of replicas
on cloud based on attack strength. Main server is isolated
from network using replica servers. Service quality features
such as response time, incoming traffic load, and load
sharing are improved due to distribution of attack and
replication of the main server throughout the cloud. We
describe our mechanism in detail and discuss improvements
made over previously existing related works. We set up an
experiment that shows significant improvement of the traffic
load on the main server as a result of utilizing DROP-FAST
Voice over IP (VoIP) services have become prevalent lately because of their potential advantages such as
economic efficiency and useful features. Meanwhile, Session Initiation Protocol (SIP) is being widely used
as a session protocol for the VoIP services. Many mobile VoIP applications have recently been launched,
and they are becoming attractive targets for attackers to steal private information. In particular, malformed
SIP messages and SIP flooding attacks are the most significant attacks as they cause service disruption
by targeting call procedures and system resources. Although much research has been conducted
in an effort to address the problems, they remain unresolved challenges due to the ease of launching variants
of attacks. In this paper, we propose a stateful SIP inspection mechanism, called SIP?VoIP Anomaly
Detection (SIPAD), that leverages a SIP-optimized data structure to detect malformed SIP messages and
SIP flooding attacks. SIPAD precomputes the SIP-optimized data structure (termed a stateful rule tree)
that reorganizes the SIP rule set by hierarchical correlation. Depending on the current state and the message
type, SIPAD determines the corresponding branches from the stateful rule tree, and inspects a SIP
message’s structure by comparing it to the branches. The SIP-optimized rule tree provides higher detection
accuracy, wider detection coverage and faster detection than existing approaches. Conventional SIP
inspection schemes tend to have high overhead costs due to the complexity of their rule matching
schemes. Experimental results of our SIP-optimized approach, by contrast, indicate that it dramatically
reduces overhead and can even be deployed in resource-constrained environments such as smartphones.
Botnets have become the main vehicle to conduct online crimes such as DDoS, spam, phishing and identity theft. Even though numerous efforts have been directed towards detection of botnets, evolving evasion techniques easily thwart detection. Moreover, existing approaches can be overwhelmed by the large amount of data needed to be analyzed. In this paper, we propose a light-weight mechanism to detect botnets using their fundamental characteristics, i.e., group activity. The proposed mechanism, referred to as BotGAD (botnet group activity detector) needs a small amount of data from DNS traffic to detect botnet, not all network traffic content or known signatures. BotGAD can detect botnets from a large-scale network in real- time even though the botnet performs encrypted communications. Moreover, BotGAD can detect botnets that adopt recent evasion techniques. We evaluate BotGAD using multiple DNS traces collected from different sources including a campus network and large ISP networks. The evaluation shows that BotGAD can automatically detect botnets while providing real-time monitoring in large scale networks.
It is often appealing to assume that existing
solutions can be directly applied to emerging engineering domains.
Unfortunately, careful investigation of the unique challenges
presented by new domains exposes its idiosyncrasies,
thus often requiring new approaches and solutions. In this
paper, we argue that the Bsmart[ grid, replacing its incredibly
successful and reliable predecessor, poses a series of new security
challenges, among others, that require novel approaches
to the field of cyber security. We will call this new field cyber?
physical security. The tight coupling between information and
communication technologies and physical systems introduces
new security concerns, requiring a rethinking of the commonly
used objectives and methods. Existing security approaches are
either inapplicable, not viable, insufficiently scalable, incompatible,
or simply inadequate to address the challenges posed
by highly complex environments such as the smart grid. A concerted
effort by the entire industry, the research community,
and the policy makers is required to achieve the vision of a
secure smart grid infrastructure.
Malicious URLs have been widely used to mount various
cyber attacks including spamming, phishing and mal-
ware. Detection of malicious URLs and identification of
threat types are critical to thwart these attacks. Know-
ing the type of a threat enables estimation of severity
of the attack and helps adopt an effective countermea-
sure. Existing methods typically detect malicious URLs
of a single attack type. In this paper, we propose method
using machine learning to detect malicious URLs of all
the popular attack types and identify the nature of at-
tack a malicious URL attempts to launch. Our method
uses a variety of discriminative features including tex-
tual properties, link structures, webpage contents, DNS
information, and network traffic. Many of these fea-
tures are novel and highly effective. Our experimental
studies with 40,000 benign URLs and 32,000 malicious
URLs obtained from real-life Internet sources show that
our method delivers a superior performance: the accu-
racy was over 98% in detecting malicious URLs and over
93% in identifying attack types. We also report our stud-
ies on the effectiveness of each group of discriminative
features, and discuss their evadability.
This article introduces a novel anomaly detection method that makes use of only matrix operations and is highly sensitive to randomness in traffic. The sensitivity can be leveraged to detect attacks that exude randomness in traffic characteristics, such as denial-of-service attacks and worms. In particular, we show that the method can be used to alert of the imminent onset of a worm epidemic in a statistically sound manner, irrespective of the worm's scanning strategies.
This article presents what we call the parallel coordinate attack visualization (PCAV) for detecting unknown large-scale Internet attacks including Internet worms, DDoS attacks and network scanning activities. PCAV displays network traffic on the plane of parallel coordinates using the flow information such as the source IP address, destination IP address, destination port and the average packet length in a flow. The parameters are used to draw each flow as a connected line on the plane, where a group of polygonal lines form a particular shape in case of attack. From the observation that each attack type of significance forms a unique pattern, we develop nine signatures and their detection mechanism based on an efficient hashing algorithm. Using the graphical signatures, PCAV can quickly detect new attacks and enable network administrators to intuitively recognize and respond to the attacks. Compared with existing visualization works, PCAV can handle hyper-dimensions, i.e., can visualize more than 3 parameters if necessary, which significantly reduces false positives. As a consequence, Internet worms are more precisely detectable by machine and more easily recognizable by human. Another strength of PCAV is handling flows instead of packets. Per-flow visualization greatly reduces the processing time and further provides compatibility with legacy routers which export flow information, e.g., as NetFlow does in Cisco routers. We demonstrate the effectiveness of PCAV using real-life Internet traffic traces. The PCAV program is publicly available.
Threads posed by Distributed Denial of Service (DDoS) attacks are becoming more serious day by day. Accurately detecting DDoS becomes an important and necessary step in securing a computer network. However, Flash Event (FE), which is created by legitimate requests, shares very similar characteristics with DDoS in many aspects and makes it hard to be distinguished from DDoS attacks. In this paper, we propose a simple yet effective mechanism called FDD (FE and DDoS Distinguisher) to distinguish FE and DDoS. To the best of our knowledge, this is the first effective and practical mechanism that distinguishes FE and DDoS attacks. Our trace-driven evaluation shows that FDD distinguishes between FE and DDoS attacks accurately and efficiently by utilizing only memory of a very small size, making it possible to be implemented on high-speed networking devices.
The Session Initiation Protocol (SIP) has been used widely for Voice over IP (VoIP) service because of its potential advantages, economical efficiency and call setup simplicity. However, SIP-based VoIP service basically has two main security issues, malformed SIP message attack and SIP flooding attack. In this paper, we propose a novel mechanism for SIP-based VoIP system utilizing rule matching algorithm and state transition models. It detects not only two main attacks, but also covers more SIP attacks. Instead of simply combining rule comparison and counting number of SIP messages, we develop secure RFC 3261 rules based on existing RFC 3261 rules, so that proposed mechanism shows 26% higher detection rate for malformed attack. Moreover, we utilize session information and define the features of each state in order to detect abnormal situations including SIP flooding. As the result, it is shown that the proposed mechanism provides not only higher accuracy, but also covering more SIP attacks including two main attacks.
Internet worms and DDoS attacks are considered the two
most menacing attacks on today’s Internet. The traditional wisdom is
that they are different beasts, and they should be dealt with independently.
In this paper, however, we show that a unified rate limiting algorithm
is possible, which effectively works on both Internet worms and
DDoS attacks. The unified approach leads to higher worm traffic reduction
performance than that of existing rate limiting schemes geared
toward worm mitigation, in addition to the added advantage of dropping
most DDoS attack packets. In our experiments with attack traffics generated
by attacking tools, the unified rate limiting scheme drops 80.7%
worm packets and 93% DDoS packets, while 69.2% worms and 3.4%
DDoS packets are dropped at maximum by previous worm scan rate
limiting schemes. Also, the proposed scheme requires less computing resources,
and has higher accuracy for dropping attack packets but not
dropping legitimate packets.
Attacks using vulnerabilities are considered nowadays a severe threat. Thus, a host needs a device that monitors system activities for malicious behaviors and blocks those activities to protect itself. In this paper, we introduce PROcess BEhavior (PROBE), which monitors processes running on a host to identify abnormal process behaviors. PROBE makes a process tree using only process creation relationship, and then it measures each edge weight to determine whether the invocation of each child process causes an abnormal behavior. PROBE has low processing overhead when compared with existing intrusion detections which use sequences of system calls. In the evaluation on a representative set of critical security vulnerabilities, PROBE shows desirable and practical intrusion prevention capabilities estimating that only 5% false-positive and 5% false-negative. Therefore, PROBE is a heuristic approach that can also detect unknown attacks, and it is not only light-weight but also accurate.
When an application program is executed for the
rst time, the results of its execution are not always predictable.
Since the host will be damaged by a malware as soon as
it is executed, detecting and blocking the malware before its
execution is the most effective means of protection. In contrast
to current research into the detection of malwares based on their
behavior while being executed, we propose a new mechanism
which can preview the effect of a program on a system. The
mechanism we developed is to represent the distinctions between
portable executable binaries. The proposed mechanism analyzes
the instructions related to the system-call call sequence in a
binary executable and demonstrates the result in the form of a
topological graph. This topological graph is called the code graph
and the preview system is called the code graph system. We have
tested various real application programs with the code graph
system and identied their distinctive characteristics which can
be used for distinguishing normal softwares from malwares such
as worm codes and botnet programs. Our system detected all
known malwares used in the experiment, and distinguished 67%
of unknown malwares from normal programs. In this paper, we
show how to analyze the effects of executable binaries before their
execution and normal softwares can be effectively distinguished
from malwares by applying the code graph.
Recent malicious attempts are intended to get financial
benefits through a large pool of compromised hosts, which are
called software robots or simply “bots.” A group of bots, referred
to as a botnet, is remotely controllable by a server and can be
used for sending spam mails, stealing personal information, and
launching DDoS attacks. Growing popularity of botnets compels
to find proper countermeasures but existing defense mechanisms
hardly catch up with the speed of botnet technologies. In this
paper, we propose a botnet detection mechanism by monitoring
DNS traffic to detect botnets, which form a group activity in DNS
queries simultaneously sent by distributed bots. A few works have
been proposed based on particular DNS information generated
by a botnet, but they are easily evaded by changing bot programs.
Our anomaly-based botnet detection mechanism is more robust
than the previous approaches so that the variants of bots can
be detectable by looking at their group activities in DNS traffic.
From the experiments on a campus network, it is shown that the
proposed mechanism can detect botnets effectively while bots are
connecting to their server or migrating to another server.
The bandwidth efficiency of Voice over IP (VoIP) traffic on the IEEE 802.11 WLAN is notoriously low. VoIP over 802.11 incurs high bandwidth cost for voice frame packetization and MAC/PHY framing, which is aggravated by channel access overhead. For instance, 10 calls with the G.729 codec can barely be supported on 802.11b with acceptable QoS – less than 2% efficiency. As WLANs and VoIP services become increasingly widespread, this inefficiency must be overcome. This paper proposes a solution that boosts the efficiency high enough to support a significantly larger number of calls than existing schemes, with fair call quality. The solution comes in two parts: adaptive frame aggregation and uplink/downlink bandwidth equalization. The former reduces the absolute number of MAC frames according to the link congestion level, and the latter balances the bandwidth usage between the access point (AP) and wireless stations. When used in combination, they yield superior performance, for instance, supporting more than 100 VoIP calls over a IEEE 802.11b link. We demonstrate the performance of the proposed approach through extensive simulation, and validate the simulation through analysis.
In this paper, we present a password stretching method based on user specific salt. Our scheme takes a similar time to stretch a password as a recent password stretching algorithm, but the complexity of pre-computation attack increases by 10^8 times and also the storage to store pre-computation result increases by 10^8 times over a recent password stretching algorithm.
From the introduction of CodeRed and Slammer worms, it has been learned that the early detection of worm epidemics is important in order to reduce the damage resulting from outbreaks. A prominent characteristic of Internet worms is the random selection of subsequent targets. In this paper, we propose a new worm detection mechanism by checking the random distribution of destination addresses in network traffic. The proposed mechanism constructs a matrix from network traffic and checks the rank of the matrix in order to detect the spreading of Internet worms. From the fact that a random binary matrix holds a high rank value, ADUR (Anomaly Detection Using Randomness check) is proposed for detecting unknown worms based on the rank of the matrix. From experiments on various environments, it is demonstrated that the ADUR mechanism effectively detects the spread of new worms in the early stages, even when there is only a single host infected in a monitoring network. Also, we show that ADUR is highly sensitive so that the worm epidemic can be detectable quickly, e.g., three times earlier than the infection of 90% vulnerable hosts.
DoS attacks use IP spoofing to forge the source IP address of packets, and thereby hide the identity of the source. This makes it hard to defend against DoS attacks, so IP spoofing will still be used as an aggressive attack mechanism even under distributed attack environment. While many IP spoofing prevention techniques have been proposed, none have achieved widespread real-world use. One main reason is the lack of properties favoring incremental deployment, an essential component for the adoption of new technologies. A viable solution needs to be not only technically sound but also economically acceptable. An incrementally deployable protocol should have three properties: initial benefits for early adopters, incremental benefits for subsequent adopters, and effectiveness under partial deployment. Since no previous anti-spoofing solution satisfies all three of these properties, we propose a new mechanism called "BGP Anti-Spoofing Extension" (BASE). The BASE mechanism is an anti-spoofing protocol designed to fulfill the incremental deployment properties necessary for adoption in current Internet environments. Based on simulations we ran using a model of Internet AS connectivity, BASE shows desirable IP spoofing prevention capabilities under partial deployment. We find that just 30% deployment can drop about 97% of attack packets. Therefore, BASE not only provides adopters' benefit but also outperforms previous anti-spoofing mechanisms.
Network topology has no direct effect on the correctness of network protocols, however, it influences the performance of networks and their survivability when they are under attack. Recent studies have analyzed the robustness of the Internet in the face of faults or attacks which may cause node failures. However, the effect of link failure or a series of link failures has not been extensively examined, even though such a situation is more likely to occur in the current Internet environment. In this paper, we propose an attack-and-failure graph model and practical techniques for attacking strategies against nodes, edges or paths in order to reect real-life attack scenarios. The resiliency of Internet topologies is examined under the attacking strategies, with various metrics including path-failure ratio and
Block-oriented sparse Cholesky factorization decomposes a sparse matrix into rectangular
subblocks; each block can then be handled as a computational unit in order to increase data
reuse in a hierarchical memory system. Also, the factorization method increases the degree of
concurrency and reduces the overall communication volume so that it performs more efficiently
on a distributed-memory multiprocessor system than the customary column-oriented
factorization method. But until now, mapping of blocks to processors has been designed
for load balance with restricted communication patterns. In this paper, we represent tasks
using a block dependency DAG that represents the execution behavior of block sparse Cholesky
factorization in a distributed-memory system. Since the characteristics of tasks for block
Cholesky factorization are different from those of the conventional parallel task model, we
propose a new task scheduling algorithm using a block dependency DAG. The proposed algorithm
consists of two stages: early-start clustering, and affined cluster mapping (ACM).
The early-start clustering stage is used to cluster tasks while preserving the earliest start time
of a task without limiting parallelism. After task clustering, the ACM stage allocates clusters
to processors considering both communication cost and load balance. Experimental results on a Myrinet cluster system show that the proposed task scheduling approach outperforms other
processor mapping methods.
Denial of service (DoS) attack on the Internet has become a pressing problem. In this paper, we describe and evaluate route-based distributed packet filtering (DPF), a novel approach to distributed DoS (DDoS) attack prevention. We show that DPF achieves proactiveness and scalability, and we show that there is an intimate relationship between the effectiveness of DPF at mitigating DDoS attack and power-law network topology.
The salient features of this work are two-fold. First, we show that DPF is able to proactively filter out a significant fraction of spoofed packet flows and prevent attack packets from reaching their targets in the first place. The IP flows that cannot be proactively curtailed are extremely sparse so that their origin can be localized-i.e., IP traceback-to within a small, constant number of candidate sites. We show that the two proactive and reactive performance effects can be achieved by implementing route-based filtering on less than 20% of Internet autonomous system (AS) sites. Second, we show that the two complementary performance measures are dependent on the properties of the underlying AS graph. In particular, we show that the power-law structure of Internet AS topology leads to connectivity properties which are crucial in facilitating the observed performance effects.
Effective mitigation of denial of service (DoS) attack is a pressing problem on the Internet. In many instances, DoS attacks can be prevented if the spoofed source IP address is traced back to its origin which allows assigning penalties to the offending party or isolating the compromised hosts and domains from the rest of the network. Recently IP traceback mechanisms based on probabilistic packet marking (PPM) have been proposed for achieving traceback of DoS attacks. In this paper, we show that probabilistic packet marking-of interest due to its efficiency and implementability vis-`a-vis deterministic packet marking and logging or messaging based schemes-suffers under spoofing of the marking field in the IP header by the attacker which can impede traceback by the victim. We show that there is a trade-off between the ability of the victim to localize the attacker and the severity of the DoS attack, which is represented as a function of the marking probability, path length, and traffic volume. The optimal decision problem-the victim can choose the marking probability whereas the attacker can choose the spoofed marking value, source address, and attack volume-can be expressed as a constrained minimax optimization problem, where the victim chooses the marking probability such that the number of forgeable attack paths is minimized. We show that the attacker's ability to hide his location is curtailed by increasing the marking probability, however, the latter is upper-bounded due to sampling constraints. In typical IP internets, the attacker's address can be localized to within 2-5 equally likely sites which renders PPM effective against single source attacks. Under distributed DoS attacks, the uncertainty achievable by the attacker can be amplified, which diminishes the effectiveness of PPM.
In this paper, we consider a load-balancing process
allocation method for fault-tolerant multicomputer systems that
balances the load before as well as after faults start to degrade the
performance of the system. In order to be able to tolerate a single fault,
each process (primary process) is duplicated (i.e., has a backup
process). The backup process executes on a different processor from
the primary, checkpointing the primary process and recovering the
process if the primary process fails. In this paper, we formalize the
problem of load-balancing process allocation and propose a new
process allocation method and analyze the performance of the
proposed method. Simulations are used to compare the proposed
method with a process allocation method that does not take into
account the different load characteristics of the primary and backup
processes. While both methods perform well before the occurrence of
a fault, only the proposed method maintains a balanced load after the
occurrence of such a fault.
Computer and Communication Security Laboratory, Department of Computer Science and Engineering, Korea University, Anam-dong, Seongbuk-gu, Seoul 136-713, South KOREA Copyright(c) 2018 Korea University CCSLAB. All Rights Reserved.