Umesh Shankar

EECS Department, University of California, Berkeley

Technical Report No. UCB/CSD-03-1246

, 2003

A critical problem faced by a Network Intrusion Detection System (NIDS) is that of ambiguity. The NIDS cannot always determine what traffic reaches a given host nor how that host will interpret the traffic, and attackers may exploit this ambiguity to avoid detection or cause misleading alarms. We present a novel, lightweight solution, Active Mapping, which eliminates TCP/IP-based ambiguity in a NIDS' analysis with minimal runtime cost. Active Mapping efficiently builds profiles of the network topology and the TCP/IP policies of hosts on the network; a NIDS may then use the host profiles to disambiguate the interpretation of the network traffic on a per-host basis. Active Mapping avoids the semantic and performance problems of traffic normalization, in which traffic streams are modified to remove ambiguities.

We have developed a prototype implementation of Active Mapping and modified a NIDS to use the Active Mapping-generated profile database in our tests. We found wide variation across operating systems' TCP/IP stack policies in real-world tests (about 6,700 hosts), underscoring the need for this sort of disambiguation.

We discuss the capabilities and limitations of Active Mapping in detail, including real-world challenges. We also present results on the performance impact of using Active Mapping in terms of time and memory.

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BibTeX citation:

@techreport{Shankar:CSD-03-1246,
    Author= {Shankar, Umesh},
    Title= {Active Mapping: Resisting NIDS Evasion Without Altering Traffic},
    Year= {2003},
    Month= {Dec},
    Url= {http://www2.eecs.berkeley.edu/Pubs/TechRpts/2003/5546.html},
    Number= {UCB/CSD-03-1246},
    Abstract= {A critical problem faced by a Network Intrusion Detection System (NIDS) is that of ambiguity. The NIDS cannot always determine what traffic reaches a given host nor how that host will interpret the traffic, and attackers may exploit this ambiguity to avoid detection or cause misleading alarms. We present a novel, lightweight solution, Active Mapping, which eliminates TCP/IP-based ambiguity in a NIDS' analysis with minimal runtime cost. Active Mapping efficiently builds profiles of the network topology and the TCP/IP policies of hosts on the network; a NIDS may then use the host profiles to disambiguate the interpretation of the network traffic on a per-host basis. Active Mapping avoids the semantic and performance problems of traffic normalization, in which traffic streams are modified to remove ambiguities. <p>We have developed a prototype implementation of Active Mapping and modified a NIDS to use the Active Mapping-generated profile database in our tests. We found wide variation across operating systems' TCP/IP stack policies in real-world tests (about 6,700 hosts), underscoring the need for this sort of disambiguation. <p>We discuss the capabilities and limitations of Active Mapping in detail, including real-world challenges. We also present results on the performance impact of using Active Mapping in terms of time and memory.},
}

EndNote citation:

%0 Report
%A Shankar, Umesh 
%T Active Mapping: Resisting NIDS Evasion Without Altering Traffic
%I EECS Department, University of California, Berkeley
%D 2003
%@ UCB/CSD-03-1246
%U http://www2.eecs.berkeley.edu/Pubs/TechRpts/2003/5546.html
%F Shankar:CSD-03-1246