Quartz 5

02 Network Security 2

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Network Security 2

Network Security 2

Malware

  • = malicious software that aims to damage computer systems and/or gain unauthorised access to them
  • May cause computer to crash or have its data deleted

Virus

  • Attach itself to another file or program
  • Remains dormant until it is executed by the user
  • Replicate to infect other computers in the network

Worm

  • Similar to virus
  • No need to attach to a file
  • Self-replicating

Trojan Horse

  • Appears as legitimate program
  • Once it gains access into computer, it runs malicious codes to cause damage to computer
  • Not replicating itself

Ransomware

  • Locks computer & encrypts the data
  • Forces user to pay a ransom to get them back

Adware

  • Unwanted software which displays advertisement on the computer

Spyware

  • Hidden program that secretly collects information and transmits information to attackers without user’s knowledge

Denial of Service (DOS)

  • Attacks network traffic to exhaust resources and bandwidth
  • System cannot fulfil legitimate requests

Distributed Denial of Service (DDOS)

  • Multiple compromised devices (botnets) to attack the system

Social Engineering Attack

  • Use of deception & trickery to convince users to provide data or to violate security guidelines
  • Precursor to another type of attack
  • Phishing: attacker sends email message that seems to come from a respected organisation. Message claims that recipient needs to provide a private information to the sender for verification purpose
  • Spam: users flooded with email or messages that act as vehicles carrying advertising material or viruses
  • Weaponisation of AI
  • Internet of Things attack
  • Cloud computing attack

Protection Scheme as a User

  • Keep computer operating system updated
  • Install anti-virus software
  • Backup & archive important documents regularly
  • Do not click on suspicious link or emails
  • Do not connect to untrusted public Wi-Fi

Protection Scheme as a Computing Professional

  • Firewall
  • = a system to prevent unauthorised access from entering a private network
  • Monitors & controls all incoming and outgoing network traffic based on a set of security rules
  • Software & hardware level
  • E.g. of filtering function: port (application), MAC (device), IP addresses (website), content (parental control)
  • Firewall
  • Limitation
  • Hackers can bypass firewall by inserting malicious attacks inside legitimate programs (e.g. emails)
  • Firewall cannot protect against internal attacks (e.g. virus in one computer in the network
  • Setting of firewall may block some legitimate program
  • Proxy Server
  • Acts as intermediary for requests from clients seeking resources from other servers
  • Hide IP address & login details
  • Control income and outgoing traffic
  • Caching machine
  • MicroNuggets: What is a Proxy Server? | CBT Nuggets
  • Virtual Private Network (VPN)
  • Unblocked censored websites
  • Adds encryption on any data transmitted in and out
  • Similar to proxy
  • While proxy controls traffic at individual application level, VPN controls all traffic that goes through the network
  • What Is a VPN and How Does It Work? (Explained for Beginners – 2026 Guide)
  • Intrusion Detection System (IDS)
  • Scans and monitors the network traffic or system for malicious activities
  • Sounds an alert when it detects an attack
  • NO action against the attack
  • Host based and Network based
  • Intrusion Protection System (IPS)
  • Differs from IDS in taking actions to block the unauthorised access or malicious packets going into the system
  • May drop packets, reset connections, sound alerts, even quarantine intruders
  • Note: for Firewall, IDS, IPS
  • Applicable to software & hardware
  • Devices can combine many security features
  • E.g. Unified Threat Management (UTM) comprises all these 3 features and many other features
  • No protection scheme is perfect; constant updates of technology is highly important

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