TRUSTED DATA COMMUNICATION AND SECURITY ISSUES IN GNSS NETWORK OF TURKEY

There are three main activities of General Directorate of Land Registry and Cadastre. These are Mapping, Land Registry and Cadastre. Geomatic Department is responsible for mapping activities. The most important projects like TUSAGA-Aktif (CORS-Tr), Metadata Geoportal, Orthophoto Production and orthophoto web services and preparation of Turkish NSDI Feasibility Report have been conducted and completed by this department’s specialists since 2005. TUSAGA-Aktif (CORS-Tr) System, serves location information at cm level accuracy in Turkey and TR Nortern Cyprus in few seconds, where adequate numbers of GNSS satellites are observed and communication possibilities are present. No ground control points and benchmarks are necessary. There are 146 permanent GNSS stations within the CORS-Tr System. Station data are transferred online to the main control center located in the Mapping Department of the General Directorate of Land Registry and Cadastre and to the control center located in the General Command of Mapping. Currently CORS-Tr has more than 9000 users. Most of them are private companies working for governmental organization. Providing data communication between control center and both GNSS station and users via trusted and good substructure is important. Additionally, protection of the system and data against cyber attacks from domestic and foreign sources is important. This paper focuses on data communication and security issues of GNSS network named TUSAGA-Aktif.


INTRODUCTION
A CORS is a Continuously Operating Reference Station.CORS can take the place of a traditional base station used in differential GNSS positing.They can give an instant position to an accuracy of a few cm and are used in many industries including Precision Agriculture, Construction, Mining, Surveying and in Scientific Research Today CORS-Tr System has more than 9000 individual users which can be grouped as Land Registry and Cadastral Offices, Governmental institutions, Licensed Surveyors, Universities and Private Companies.All user have chance to get good services from Geomatic Department via detailed web page, SMS and email message.More over call center (444) support is available in case of any problems on the field for 24/7.This paper presents trusted data communication infrastructure and security issues of CORS-Tr system in Geomatic Departments.

CORS-Tr DATA COMMUNICATION
A GNSS network consists of several GNSS stations interconnected by reliable communications to enable real time computations and control.Each station has a cabinet which contains a receiver, an antenna, communication devices, small data storage, power supply, accumulator and so on.In most cases a computer is installed additionally for data transmission and control.It also contains a user interface which is required to configure and maintain the network.This may be realized remotely for example by radio communication, mobile phones or via internet connection.
In Turkey Turk Telekom Backbone for CORS-Tr data communication is available.CORS-Tr system has VPN tunel between reference station and control center as primary data communication and 3G APN tunnel as secondery.User connections are supported by APN tunnel by all three GSM Operators in Turkey.And all RTK correction send to user via an APN tunnel.Data communication structure is shown in section 3.3 Networks topic (Figure 3).

CORS-Tr SECURITY ISSUES
Cybersecurity is the body of technologies, processes and practices designed to protect networks, computers, programs and data from attack, damage or unauthorized access.In a computing context, the term security implies cybersecurity.Elements of cybersecurity includes [2]: Disaster recovery / business continuity planning • End-user awareness and education.

Applications
In CORS-Tr system, we have Network RTK correction, networks DGPS correction, web online processing services and RINEX datas to provide our users.All applications are shown below.

Networks
We have two different networks in Geomatic Department.

Our Experience and Business continuity planning
Of course CORS softwares including operating system and hardware, normally has their own firewall and some security issues with many applications.But we faced many problems since CORS-Tr established and these problems are briefly described below.

Lack of IT Personnel:
Only Surveying Engineers and Surveying technicans were avaliable to operate CORS-Tr system, user membership and payment issues and to support users.There wasn't any IT staff to control system in case of a technical problem.Highly qualified geoinformatics personnel dealt with technical problems such as system freezing, communication bandwidth saturation or even exchange of broken hardisk.

DDOS Attacks:
In summer season of year 2013 which mapping applications on the field by using CORS-Tr are very dense, we faced a very hard DDOS attack by an unknown source.DDOS attacks were continued for approximately 3 months, every day between 10 a.m. and 12 a.m.

Awareness of Internal Users:
Internal system users who use computers that has virus, malware, trojan.etc.Internal users who used virus contaminated USB to connect system servers or unsafe remote desktop connection caused danger for the system.Unfortunately Institutional anti-virus system was unable to protect CORS-Tr system.Internal user's awareness on security issues should be increased.

Awareness of External
Users: Some external users somehow adjusted their GNSS instrument settings to send more than five request in a second to connect CORS-Tr system.These requests interrupted other user connections and overloaded data communication bandwidth.Some external users shared their own password and user name with other users which cause conflict between the users.Another problem caused by external users is unnecessary attempts for connection.Although their term has finished many external users, try to connect to the system.

IMPROVEMENTS
Measures taken to establish trusted service in CORS-Tr system usage in terms of security requirements after experienced problems are:

CONCLUSION
At the beginning of TUSAGA-Aktif project we thought that project was considered geodesy related works only.Today we understood that TUSAGA-Aktif is not only a geodesic related work but also Information and Communication Technology work.
As a result today CORS-Tr have trusted data communication infrastructure, protected information and services by updated software and hardware including security devices and has more powerful user support.
[1].Continuously Operating Reference Stations GNSS Network Project called CORS-Tr (TUSAGA-Aktif in Turkish) has begun in 2006 as a research and development project of The Scientific and Technological Research Council of Turkey (TUBITAK) by supporting financial side, Istanbul Kultur University (IKU) as a project implementer and The General Directorate of Land Registry and Cadastre (TKGM) and General Command of Mapping (HGK) including as joint customers.CORS-Tr project completed in 2009 and operated by TKGM and HGK collectively.Until 15 June 2011, it was operated free of charge for test purposes.Since then it has been operating as a paid service and price is determined by Inter Ministries Mapping Coordination and Planning Committee (BHİKPK) and confirmed by both Ministers who are Environment and Urbanization Minister and Defense Minister.TUSAGA-Aktif (CORS-Tr) System, serves location information by cm level accuracy in Turkey and TR Nortern Cyprus in few seconds, where adequate numbers of GNSS satellites are observed and communication possibilities are present.No ground control points and benchmarks are necessary.CORS-Tr System includes 146 permanent GNSS stations.Station data is transferred online to the main control center located in the Mapping Department of the General Directorate of Land Registry and Cadastre and the second control center located in the General Command of Mapping.

Figure 2 -
Figure 2-TUSAGA-Aktif Information to be backed up and to be archieved

Figure 3 -
Figure 3-Geomatic Department Network Design Main applications like Network RTK correction, networks DGPS correction and provision of RINEX data to the our users and SQL databases are protected by extra security software for cyber attacks.• In CORS-Tr network, servers and end points are protected by a software from inside and outside cyber attacks.• User awareness of CORS-Tr usage was increased by 444 call center, SMS message, Social Media and Local trainings.And also customer satisfaction are surveyed regularly.