Tuesday, November 25, 2014

Information Security Basics Part 1: Security Models

image source: http://prmgsecurity.com/wp-content/uploads/2012/12/shutterstock_103173656.jpg

Security means different thing to different people.

To a home user, security is antivirus protection.  The objective is to keep the electronic device free of Malware of Rootkit so that the device can operate “normally”.  It can also mean safe web site access to bank and/or other financial institutes such that their financial account will not be compromised.  Or in some case, celebrities may want to protect their private pictures or videos.  Failure to protect the user device or user’s financial account can lead to monetary loss.  Identity thief is also a major concern for home computer users.

To the government, security, I think will be the protection of sensitive data and the continuous operation of the various departments and agencies. Around November 16, 2014, the U.S. State Department website was compromised.  And it is the 4th U.S. government agency to announce a breach of their computer systems within a few weeks’ time.  Failure to protect the government’s computer systems can lead to lost of human lives.

To the private sector, security is the protection of data which can be intellectual properties or customer’s financial and private information such as health history, social security number.  Often times company has the office of Chief Security Officer responsible for the “security” and compliance of security rules of the company such as HIPAA for the health sector or Gramm-Leach-Bliley Act for the financial sector. 

Regardless what security means for us, we can always look at security with the following model.

The CIA Triad
This is the most common security model for information systems. This model is used to develop security policy, identify area of security risk and most of all to deploy measurements to mitigate the identified risk.

CIA stands for:
  • Confidentiality
  • Integrity 
  • Availability
image source: http://securitytoolkit.files.wordpress.com/2012/04/cia3.jpg

I like this diagram because besides showing the 3 elements of the CIA triad, it is showing data in the middle.  Most of the the time security are applied to protect data.  Social Security number is a form of data, bank account is a form of data, and intellectual properties is another form of data.  Conceptually, these 3 elements are applied toward data.  In other word, we should show as:
  • Confidentiality of the data
  • Integrity of the data
  • Availability of the data
Confidentiality means data can only be accessed by the authorized entity.  The owner of the data decided who can gain access to the data.  Access means to read, to modify or to delete the data.  The most basic form of providing confidentiality will be password protection.  To gain access to a personal computer or device we need to provide the user name and password.  Password can be as simple as a 8 character text string or it can be a X.509 certificate.  Also, there can be multiple level/factor of authentication where besides a password user will have to provide an authorized token.  For multi-level authentication user will have to provide:
  • Something you know - password
  • Something you have - RSA Token
  • Something you are - biometric

Another way to provide confidentiality is encryption.  To be satisfy regulatory requirement some companies will require the company issued personal device to turn on encryption so in case the device is lost, there is one level of safe guarding the data that is in the personal device. For BYOD, come companies can provide the ability to wipe out the data on a device remotely.

Integrity means data cannot be modified by unauthorized entity as well as the reliability of the electronic device that is storing the data.  With a flip of a bit in the storage device can make a bank account to reflect the wrong amount of money that is available.  As with object storage Swift, data are by default store in 3 different devices and there is a audit task to make sure the data are in tack.  Data replication technique such as RAID (either software or hardware) is another way to provide a means to ensure the integrity of the data.

One basic form of data integrity check for the integrity of the data is to use of a hashing function.  In networking, an Ethernet frame has a CRC value at the end so that when the frame is received, it can be checked with to see if the frame is altered during transit.  System Administrator are familiar with the MD5 hashing value of an ISO image. 

Password protection and encryption also help to prevent the data to be modified by unauthorized entity.

Availability means data can be accessed when needed.  Have you ever hit the wrong button on your computer and deleted all the Emails in your inbox?  Or have you accidentally delete the files in a directory?  In these cases backup comes to the rescue.  It is important to test the recovery of the backup data. Very often data is backup but when we have to make sure the backup tape is not empty or being over written by later backups. If you are a System Administrator you must know this famous line "Test your backup regularly!"

Most companies have a disaster recovery plan such that if data is lost due to fire, earth quake or terrorist attack data can be restored according to the expected Recovery Time Objective (RTO) and Recovery Point Objective (RPO).  It is very important to test out the recovery plan just like testing the recovery of the backup data.

Data delete by unauthorized entity is of course the basic form of attack in the area of availability.  Another form will be denial-of-service (DOS) attack.  We can easily imagine what will happen to a company if consumers are not able to access a online shopping website before Christmas because some attacker launched a DOS attack on that website.

Which one is more important?
While all 3 elements of the CIA triad are important, different organization will have different element as the most critical area.  For example, in health care industry confidentiality will be the most important element.  In bank or financial institutions, integrity will be the most important element.  Lastly as stated for online shopping/e-commerce based organization, availability will be the most important element.

Related Post:
Information Security Basics Part 2: Defense in Depth
Information Security Basics Part 3: Cryptography 
Information Security Basics Part 4: Public Key Infrastructure (PKI)


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