Security - Telenor

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The Policy Control Center
An implementation of a policy enforcement
mechanism described in the previous section
is currently being developed at Telenor R&D,
called a “Policy Control Center”. The Policy
Control Center is controlled by a secured “Policy
Control Center Server” located at the home/
corporate network.
For communication between mobile terminals
and this server (between the Policy Control Center
and the Policy Control Center Server) LDAP
over SSL is currently being used with both client
and server side certificates.
The Policy Control Center Server contains different
policies for different users, as well as different
policies for different network configurations.
When a mobile terminal is outside the corporate
network, we enforce a stricter security
policy compared to the case where the mobile
terminal is connected via a physically “secured”
cable inside the corporate network (and behind
the corporate firewalls).
However, when introducing the concept of Multiple
shared virtual VPNs as described earlier
where a physically secured cable is simply not
available, you need to introduce a security policy
similar to the one used when connected directly
to the Internet.
The initial implementation of the Policy Control
Center was running on Linux, where we have
investigated among other things the following
security technologies to be integrated and used
to secure the mobile terminal:
• Local firewall service through the use of
“Ipchains”. This is a rather basic packet filtering
firewall available on Linux systems.
• A simplified network Intrusion Detection System
by a combination of “Ipchains” and “Port-
Sentry” [2], allowing dynamical blocking of
unauthorised network attacks using TCPwrappers.
• Host based Intrusion Detection System
through the use of “LIDS” [3], the Linux
Intrusion Detection System.
• Integrity protection on the PCC itself as well
as on all system critical parts of the file system
through the use of “LIDS” [3]. LIDS
enables the strict enforcement of read-only
policies, making selected parts of the file system
read-only or append only even for the
superuser (root).
• VPN access through the use of “FreeS/WAN”
[4], a Linux IPsec implementation.
• Disk encryption mechanisms.
All policies need to be verifiable. To verify that
the policies defined are actually implemented
correctly on the mobile terminal, we need to
build our implementation upon strong cryptographic
protection mechanisms as much as possible.
All software components to be used as part
of the Policy Control Center need to be integrity
protected so that as many attempts as possible on
modifying and bypassing the protection mechanisms
are discovered. Successfully bypassing
of the Policy Control Center could mean that a
compromised mobile terminal is able to access
the internal corporate network.
We are currently investigating the possibility of
integrating local information protection through
further use of disk encryption, incorporating the
use of smartcards and PKI systems as well as all
other security mechanisms required covered earlier
in this article, in order to achieve the best
possible security for the future users of Internet
mobility.
Our current work covers the development of a
pure JAVA version of the Policy Control Center,
making sure that all kinds of different terminals
running JAVA may be secured using our PCC.
Although the PCC implementation is platform
independent, the policies themselves are however
highly platform dependent.
Challenges currently under investigation include
for example:
• How to most efficiently and securely write
and handle the policies for different platforms;
• How to protect the Policy Control Center
itself from unauthorised modification and
bypassing attempts;
• Making sure the right policy is selected automatically,
how do you know where you are?
Conclusions
Keeping a computer system connected to the
Internet secure is a challenging task even for
experienced security personnel. New software is
frequently being introduced, often with little or
no concern for potential security implications,
and new vulnerabilities are constantly being
found both in old and new software. In particular,
without an open development model, mistakes
made before are bound to be repeated over
and over again without the customers ever hav-
Telektronikk 3.2000