Transcript Covert channel

Design of the multi-level security network switch
system which restricts covert channel
Conference: Communication Software and
Networks (ICCSN), 2011 IEEE 3rd International
Conference on
Authors: Xiong Liu, Haiwei Xue, Xiaoping Feng,
Yiqi Dai, Department of Computer Science and
Technology, Tsinghua University, Beijing 10084,
China
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Covert channel
• In computer security, a covert channel
is a type of computer security attack
that creates a capability to transfer
information objects between processes
that are not supposed to be allowed to
communicate by the computer security
policy.
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Multi-level Security Local Area
Network system (MSL)
• The low level host can send data packet to
high level host, but high level host cannot
send data packet to low level host.
• TCP/IP SYN/ACK packet cannot be sent back
in the above mechanism. So it must allow
the sending of SYN/ACK.
• The SYN/ACK may become a loophole for
the covert channel.
Low level
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High level host
System architecture
• Monitor in each hosts
• Controller
• Filter
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System architecture- Monitor
• The system can monitor the hosts’ actions to
specify the hosts’ security level by the
monitors.
• The user must install the monitor in their
computer.
• Monitor communicate to the controller.
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System architecture- controller
• Functions:
– Host registering: Make sure that all the hosts and
switches connected to the network are
authorized.
– Flow computing: Compute the packet’s flow
path based on the network’s topological
structure. It can make sure all of the data flow
paths are compatible with the system’s security
policy Level: 2
Level: 3
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System architecture- controller
(cont.d)
– Flow updating: When the flow path has been
computed, the Controller updates the flow tables
of switches which locate on the path to set up it.
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System architecture- filter
• Content check module
– Level 1: Check the data field and flags
field.
– Level 2: Check the unused fields and
optional field.
– Level 3: Check the sequence number and
acknowledgement number.
– Level 4: Check the covert channel which
uses packet retransmission or packet loss
to send information.
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Experiment
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Conclusion
• This paper proposed a design of multilevel security network switch system
which can restrict covert channel.
• The design can guarantee the
availability and security of the
information exchange among hosts in
multi-level security network system.
The experiment showed that the
design is available.
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Reference
• http://en.wikipedia.org/wiki/Covert_cha
nnel
• [L-BLP security model in local area
network],http://www.ejournal.org.cn/C
N/abstract/abstract44.shtml
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