Preventive Measures

Aimed at stopping a hazardous event from occurring. When you're trying to stop/prevent something from happening by putting in preventative measures (do something) to stop the thing that could happen.

Preventative measures used on a computer:

  • Access Rights
  • Firewalls
  • Passwords
  • Encryption
  • Acceptable use policy
  • Physical Security (e.g. locking rooms)

Detective Measures

Aimed at detecting when data has been corrupted or systems have been compromised. These measures are focused on discovering or detecting unwanted happenings before they occur.

Detective measures used on a computer:

  • Virus checking software
  • Firewall software
  • Fire alarms
  • Audit trails

Corrective Measures

Aimed at correcting or restoring the system after problems have occurred due to an event or disaster.

Corrective measures used on a computer:

  • Backup & restore features
  • Redundant hardware/fail-over
  • Disaster recovery procedures


Security Precautions

Access rights

User access rights should be set for disks, folders and files so that users can only access what they need to.

Examples of use:

  1. At school, you can probably only read files on a shared are but not edit them; this is Read-Only access. On the other hand, teachers will have Read-Write access which allows them to edit these folders. Some folders you won't even be able to see.
  2. In a work environment, the Accounts staff will have access to payroll details but other departments will not because the files will have access rights which only work for the right people. The Data Protection Act says that employees must keep personal data secure which means that setting appropriate access rights is not only a good idea but also a legal responsibility.


There are devices that can read network transmissions from the cables, without needing to be plugged into the network, just by scanning the emissions. Also anything transmitted over a network can be intercepted and read.

Both of these can happen without leaving any trace so nobody would know it happened.

One way of stopping this unauthorized access to data is to encrypt anything sent on a network. Encryption changes the data before it is transmitted so it can only be deciphered by the appropriate key. To anyone intercepting the message it would be unintelligible.

An example of this is when you buy something on the internet or use internet banking, instead of the HTTP in front of a domain name, it changes to HTTPS. It works in the same way as HTTP but is encrypted so your payment details are secure.

Password Protection

In a networked environment such as a school or a company, many of the computers are used by more than one person. Even if employees have their own computer it may be in an open plan office. The easiest way to stop unauthorized access to your computer or your files it to use a combination of a username and a password.

A password should never be shared with friends or stuck on a post-it note under the keyboard!!!

The password should be strong too.

A strong password needs to:

  • be difficult (not easy to guess)
  • contain letters, numbers & symbols
  • be at least six characters long

For additional security against people trying lots of different passwords to get into someones account, the account can be locked after a certain number of failed attempts.

Network Policies

Backup & Restore Procedures

A backup is a copy of a users' files, which can be restored in the event of files getting corrupted or deleted. Backup copies must be made regularly; how often depends on the nature of the system to a certain extent.

In some businesses a daily backup may be sufficient, but in others they can be backed up every hour or weekly.