GCSE (9-1) Computer Science
Mark Scheme
J277/01: Unit 1.4 DoS & Data Interception
Question Answer Marks Guidance
1a Flooding 1
1b Packet Sniffer 1
Allow: Sniffer.
1c Bandwidth 1
Allow: Processor / RAM / Memory.
2a Denial of Service / DoS 1
Do not allow: DDoS (Distributed) - The question specifies a single IP address, which implies a standard DoS, not a distributed one.
2b
  • The attacker sends more requests than the server can handle (flooding). (1)
  • This consumes the server's bandwidth / CPU cycles / RAM. (1)
  • The server cannot process legitimate requests from real customers (causing a timeout/crash). (1)
 3
Simply saying "It slows the computer down" is NE (Not Enough). Must reference consumption of resources.
2c One from:
  • Loss of revenue / sales.
  • Loss of customer trust / reputational damage.
  • Costs to fix the server.
 1
Do not allow: "Data theft" or "Installing viruses". DoS attacks generally do not involve stealing data.
3a
  • The hacker uses packet sniffing software... (1)
  • ...to monitor/capture the data packets travelling across the wireless network. (1)
 2
Key concept: "monitoring" or "capturing" traffic as it travels.
3b
  • A Firewall protects the computer/device from unauthorised access (incoming/outgoing traffic). (1)
  • It does not protect data once it leaves the computer and travels across the network/internet. (1)
 2
Misconception: Firewalls are "gatekeepers" for the device; they cannot stop someone sniffing packets on the wire/airwaves outside.
3c
  • It uses Encryption (HTTPS). (1)
  • This scrambles the data so if it is intercepted, it is unreadable / meaningless (without the key). (1)
 2
Do not allow: "It stops the data being intercepted." (Encryption stops understanding, not interception).
4a
  • DoS Purpose: To shutdown a web server / prevent access for legitimate users. (1)
  • Interception Purpose: To steal confidential information / passwords / data. (1)
 2
Clear distinction required: Disruption vs. Theft.
4b DoS Prevention:
  • Firewall (to blacklist the flooding IP). (1)
  • Bandwidth limits / Rate limiting. (1)

Interception Prevention:
  • Encryption / VPN. (1)
  • Not using public Wi-Fi / Using wired connections. (1)
 4
Ensure prevention matches the attack.
"Strong Passwords" is NE for Interception.
"Anti-virus" is NE for DoS.
OCR 2026