Abstract-One of the key benefits of using intrusion-tolerant systems is the possibility of ensuring correct behavior in the presence of attacks and intrusions. These security gains are directly dependent on the components exhibiting failure diversity. To what extent failure diversity is observed in practical deployment depends on how diverse are the components that constitute the system. In this paper we present a study with operating systems (OS) vulnerability data from the NIST National Vulnerability Database. We have analyzed the vulnerabilities of 11 different OSes over a period of roughly 15 years, to check how many of these vulnerabilities occur in more than one OS. We found this number to be low for several combinations of OSes. Hence, our analysis provides a strong indication that building a system with diverse OSes may be a useful technique to improve its intrusion tolerance capabilities.

One of the key benefits of using intrusion-tolerant systems is the possibility of ensuring correct behavior in the presence of attacks and intrusions. These security gains are directly dependent on the components exhibiting failure diversity. To what extent failure diversity is observed in practical deployment depends on how diverse are the components that constitute the system. In this paper, we present a study with operating system's (OS's) vulnerability data from the NIST National Vulnerability Database (NVD). We have analyzed the vulnerabilities of 11 different OSs over a period of 18 years, to check how many of these vulnerabilities occur in more than one OS. We found this number to be low for several combinations of OSs. Hence, although there are a few caveats on the use of NVD data to support definitive conclusions, our analysis shows that by selecting appropriate OSs, one can preclude (or reduce substantially) common vulnerabilities from occurring in the replicas of the intrusion-tolerant system. ‡ A specific type of bug, regarding security, is usually called a vulnerability. Once a vulnerability is discovered, it can be maliciously exploited. If the exploited vulnerability leads to the software system deviating from its intended requirements or security policy, then the system is deemed to have failed. The system can fail on a single or combination of the following security properties: confidentiality, availability, and integrity. In the rest of this paper, we will use the terms fault and vulnerability interchangeably. 736 M. GARCIA ET AL.faulty. To satisfy this provision, system components need to exhibit failure diversity, that is, the probability that a majority of components fail at the same time should be negligible (or else the system as a whole will fail). This failure diversity assumption is easier to justify when one is concerned with accidental faults, such as power outages, disk crashes, or message corruption due to noise in communication lines. However, for design faults of any kind, including security vulnerabilities, the assumption is difficult to guarantee. If multiple components contain the same vulnerabilities, then a single attack can compromise all of them, therefore defeating the aim of intrusion tolerance system in providing improved security.To reduce the probability of vulnerabilities existing in more than one component, design diversity [3] can be employed: each component uses diverse software to perform the same functions, with the expectation that the differences will reduce the occurrence of common vulnerabilities, that is, vulnerabilities that exist in more than one system. Byzantine fault-tolerant replication often suggest the use of replica diversity (e.g., [4][5][6][7][8][9][10][11][12][13][14]), under the (sometimes implicit) assumption that they exhibit failure diversity. In this work, we want to empirically assess to what extent failure diversity is exhibited in a complex category of OTS software, namely operating systems (OSs).We focus our study on OS because they are a...

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Distributed reflection denial of service (DRDoS) attacks are widespread on the Internet. DRDoS attacks exploit mostly UDP-based protocols to achieve traffic amplification and provide an extra layer of indirection between attackers and their victims, and a single attack can reach hundreds of Gbps. Recent trends in DRDoS include multiprotocol amplification attacks, which exploit several protocols at the same time, and carpet bombing attacks, which target multiple IP addresses in the same subnet instead of a single address, in order to evade detection. Such attacks have been reported in the wild, but have not been discussed in the scientific literature so far. This paper describes the first research on the characterization of both multiprotocol and carpet bombing DRDoS attacks. We developed MP-H, a honeypot that implements nine different protocols commonly used in DRDoS attacks, and used it for data collection. Over a period of 731 days, our honeypot received 1.8 TB of traffic, containing nearly 20.7 billion requests, and was involved in more than 1.4 million DRDoS attacks, including over 13.7 thousand multiprotocol attacks. We describe several features of multiprotocol attacks and compare them to monoprotocol attacks that occurred in the same period, and characterize the carpet bombing attacks seen by our honeypot.