1. 1 3 Computing System Fundamentals 3.4 Networked Computer Systems

2. 3.4.5 Data Integrity and Security

3. 3 Security and integrity Both relate to protection of data during storage and/or transmission Security – prevention of deliberate theft, damage or unauthorised access. Integrity – maintenance of accuracy despite natural events (hardware failure, data entry error, fire...)

4. 4 Physical security Networks create security problems - physical security can be maintained by: ‣ an administrator not leaving an office unattended when logged on to a network server, ‣ security code on the door, ‣ CCTV cameras.

5. 5 Logical security Logical security is built into operating systems, preventing unauthorised access User ID/passwords deny access to systems. Permissions/privileges limit the scope of actions people can take with the system e.g. a low-level clerk might not be able to copy sensitive files to a local flash drive.

6. 6 Logical security Passwords must be: ‣ of a reasonable length (6 characters or more), ‣ hard to guess (not a name or word) and ‣ containing symbols besides alphabetic characters. e.g. r@66IT.al1urer@66IT.al1ure

7. 7 Hacker or cracker? A hacker is someone who is talented at and enjoys solving technical problems. A cracker tries to break into networks for which they have no authorisation - they may come from outside the organisation or be internal e.g.. disgruntled employees.

8. 8 Security records The network OS maintains a detailed security log. Alert systems give details of who has accessed what parts of the system and when. Social ‘hacking’ is now the greater security risk.

9. 9 Encryption Especially sensitive data (financial transfers, police data on suspects, government military secrets) should be encrypted for transmission and storage. Encryption is the mathematical scrambling of data into apparent random noise (which only the intended recipients can decrypt). Early codes required the transmission of a key by some other means.

10. 10 Encryption Early encryption (pre-1990’s) required the transmission of a key by some other means. Modern encryption is asymmetric - data (e.g. credit card number) can be encrypted with a public key and can then only be decrypted by the holder of the corresponding private key. Examples: secure web browsing (https), encrypting e-mail, WPA encryption of wifi networks.

11. 11 Backup Important data should be regularly backed up and stored in a safe place (off-site if it is vital to the continued operation of the business). Good advice is: ‣ 3 copies of all data, ‣ 2 different media and ‣ 1 of them offsite.

12. 12 Checking integrity Check digits and parity bits. Batch totals and checksums. Error detection and correction algorithms are complex and may be part of network protocol. Some of the above allow self-correction; generally, error detection leads to a request for retransmission.

13. 13 Quality of transmission Cables are less susceptible to interference (‘noise’) than radio (although mains electricity cable nearby may interfere). Digital signals are less prone to noise than old analogue ones, so can use narrower frequency ranges and faster transmission (less retransmission) over radio. Optic fibre is most reliable e.g. not susceptible to lightning strikes.