An Internet-Wide Distributed Security Protocol and Implementation

José M. Vidal

University of South Carolina


As the Internet becomes the backbone of a growing part of the world's business and social activities, our need to guarantee its safety becomes a pressing concern. One of the biggest risks to the Internet's survivability is the growing number of distributed and automated attacks by malicious intruders. The security industry has concentrated on the development of automated security programs that detect problems at a specific computer. These programs never use the Internet as a communications medium, except when downloading updates from a central server---usually owned by the same company that produced the program. Security consortiums, on the other hand, concentrate on the publication of security alerts aimed at system administrators. None of these approaches manages to leverage the distributed automated nature of the Internet to serve as a vehicle for its own survival. Meanwhile, more and more security incidents consist of a large series of widely distributed exploits, involving numerous systems, networks, operating systems and applications. Intruders often compromise multiple systems when they attack a target site. We know that at each compromised system there may be signs of intrusive activities which, if gathered automatically and analyzed in a timely manner, could lead to the discovery of the attack. However, the domain languages and interaction protocols that are needed do not exist. The industrial security vendors are not interested in the development of an open automated system that could eliminate the need for their products.

The goal of the proposed research is the development of an open Internet-wide distributed security protocol that will allow systems to dynamically detect and respond to security threats that would be otherwise invisible to the individual system (e.g., a computer, a LAN, or a firewall-guarded corporation). We propose to develop: languages for describing suspicious events, interaction protocols for the exchange of these events, and decision processes that agents can use for choosing which action to take. The proposed prototype system will distinguish and deal with distributed attacks on the infrastructure as they happen. It will also form a platform for future research into the dynamic identification and eradication of new attacks. We believe that our interaction and content protocols will serve as enablers to distributed intrusion detection in the same way that HTTP and HTML served to enable the web.

The proposed project will extend our ongoing efforts in this direction. Over the last year and a half we have built a prototype system that implements some of the basic ideas presented in this proposal.

Current System

Figure 1: Architecture of our current prototype system. Each agent is responsible for a set of computers. The log files produced by the computers are first analyzed by a log file analyzer. Any detected problems become goals for the agent to act on.

We have designed and implemented a security framework that provides a service for retrieving the information from a distrusted network. This information is then used to detect intrusions on hosts. The architecture of the project is shown in Figure 1. We assume that each domain is represented by an agent. All computers in a domain submit their log files to a central database for that domain. These log files are analyzed by a log analyzer which reports any suspicious events to the agent. The log analyzer merely performs some simple string-matching functions in order to pick out those log entries that are out of the ordinary, or those that report on the current system's status. We expect that the agents will reside in the same machine that runs the firewall for a group of trusted hosts, such as the machines within a company or university.

While our current implementation ties the agents to specific intrusion detection and log analysis software, the basic architecture allows us to wrap our agents around any of the existing distributed security frameworks. This means that users would not need to abandon their current software systems if they wanted to migrate to our system. They would only need to implement an agent that translates their security events to work with our system.

In the context of our application an agent is defined as an encapsulated software entity with its own state, behavior, thread of control, and ability to interact and communicate with other entities---including people, other agents, and systems. An agent is autonomous in its action and communicates with other agents using the FIPA-ACL. The agents are implemented using FIPA-OS. Both of these are described in the next section.

Proposed System

While our prototype system has been shown to work in a laboratory setting, several barriers must be cleared for the system to be eligible for Internet-wide deployment and use.

  1. The agents must use a published, semantically-precise language for describing the events. The list of possible vulnerabilities must be constantly updated by some industry-wide consortium.
  2. The agents must use a published and standardized protocol for communication.
  3. The knowledge that the agents employ to handle messages must be represented in such a way that it can itself be sent as a message.

Experience has shown us that a technology must be easy to describe and implement in order for it to succeed in the Internet. That is, new technologies take the form of standards' documents that describe a protocol or data format. If these are simple and useful then many implementations will appear and, eventually, the laws of increasing returns will take over. As such, the proposed system will maintain the interaction protocols as simple as possible while, at the same time, adhering to most widely used Internet standards.

Technologies Used

Our wish to adhere to the most widely-used Internet standards had to be tempered by the reality that many of the technologies we require have not yet reached maturity. Still, we plan to use the best of what is available at this time. The technologies we plan to use include the Common Vulnerabilities and Exposures, RDF, DAML, and FIPA. We provide a quick overview of these technologies in the next sections.


Figure 2: Diagram of the proposed architecture. The interaction between the agents will be governed by our interaction protocols.

The proposed system has an architecture that, at a high level, is similar to our current system. However, the details are very different. Our proposed research focuses on three areas: the development of a language for describing suspicious events, the development of a suitable interaction protocols, and the development of a method for handling the exchange of knowledge about how to recognize and handle security threats via communications with other agents. These three areas are detailed in the next sections.

The architecture for our proposed system is shown in Figure 2. As with our current system, we envision having one agent handle all the log files for each domain. A domain can be, for example, a company, a university, or some other LAN. As before, the log files are analyzed using one of the available log analyzer which simply strips out all the uninteresting and duplicated information. The results are then all placed in an event log database. The agent monitors the event log database for suspicious events. Notice that our architecture supports the reuse of existing distributed intrusion detection systems by simply wrapping their results with one of our agents or by modifying the systems to use our event language and interaction protocols.

We envision a system where millions of agents share information, either directly or indirectly, with each other. As such, scalability is a central concern for us. Our protocols are based on a peer-to-peer model where no one agent acts as a central control. Furthermore, we envision the connectivity of the resulting graph to be rather low. That is, each agent should not have to correspond with more than a few hundred other agents. There are, of course, some bootstrapping concerns with these types of systems. The biggest problem is determining how agents find each other. This problem is usually solved with the use of a hierarchical name-resolution system, as used, for example, in DNS. We will investigate the viability of this type of hierarchical system as well as the peer-based discovery mechanisms used by Gnutella and JXTA. We believe that a peer-based discovery mechanism will work better alongside the reputation management protocols we will develop.

The authentication and verification problem will be handled in our prototype system with the use of a public-key signature mechanism to verify the identify of the originator of a message. That is, all messages can be signed, if desired, and the receiving agents will be able to verify the signatures by accessing a well-known and trusted key server. As such, we propose to leverage the existing public key infrastructure rather than develop new methods ourselves.

The agents will use FIPA ACL as the wrapper language and our own RDF-based Event language as the content language. We have again chosen to use FIPA ACL since we feel it is the only well-known language with carefully defined semantics. Unfortunately, this combination is not enough to properly define a system so we will also be defining added interaction protocols. We should also note that our choice of FIPA ACL does not preclude the use of common distributed programming tools such as SOAP, Java RMI, or CORBA. FIPA ACL is defined at a higher semantic level than these tools. In fact, bindings exist for using RMI and IIOP---CORBA's transport protocol---as transport layers for FIPA ACL. We expect that SOAP bindings will soon appear and, in fact, we expect to use HTTP/SOAP as the underlying transport mechanism for our messages since it is the least likely to be blocked by a firewall.

Our agent implementations will use a rule-based system such as Jess since it will give us the flexibility we need to implement the domain knowledge. The agents will use the knowledge base to determine what to do with a message they have received and what messages to send. The knowledge base allows agents to perform signature-based and anomaly-based intrusion detection as well as to maintain cooperative relationships with other agents.

Impact of Research

The implementation of the proposed system will result in both short and long term benefits. The short term benefits include the development of a distributed, robust, open, intrusion-detection and management system. If successful the system will offer unprecedented automatic management of security problems on the Internet. It will be able to discover anomalies and possible attacks which would be impossible to detect from any single location in the Internet. Currently, the most troublesome security problem have an automated aspect to them, that is, they rely on autonomous programs to do some of the work. As the popularity of these automated attacks grows in number we must start to use similar and even more sophisticated techniques in order to contain them.

The long term benefits of the proposed project include the generation of a wealth of data which will a ready candidate for the application of data mining techniques. Specifically, we envision the possibility of using data mining techniques, along with some machine learning algorithms, in order to develop algorithms which can discern new distributed attacks and generate rules for their detection and defeat. The proposed project will also foster the future development of scalable reputation mechanisms. In this project we propose to build some rudimentary reputation management mechanisms which will allow agents to form opinions of other agents and pass these around. However, a more flexible system would extend this basic research and allow the agents to dynamically generate trust measures, form alliances, sign contracts, form trust relationships, etc. These type of sophisticated social contracts, when better understood, will greatly aid in reducing the amount of communication needed. As such, they will aid in allowing the system to scale up to millions of agents without any bottlenecks.

Finally, we stress once again that we view the main contribution of the proposed work as the development of easy-to-use but powerful event languages and interaction protocols for distributed security management. Our prototype implementation is only meant to be a testbed for our ideas. We want to merge current research from multiagent systems, ontologies, and security in order to come up with the equivalent of HTTP/HTML for distributed security systems.

Jose M Vidal-
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Last modified: Sat Jun 8 15:00:35 EDT 2002