Network Security

Service Denial Attack: DoS and DDoS

A Denial of Service (DoS) attack attempts to make a system or network service unavailable by exhausting its resources. A Distributed Denial of Service (DDoS) attack extends this concept by generating attack traffic from multiple compromised systems.

Key Characteristics

• Targets system availability rather than confidentiality or integrity.
• Consumes bandwidth, CPU, memory, or connection tables.
• Often asymmetric: attackers spend fewer resources than defenders.

Common Attack Types

• Network-level floods: ICMP, UDP, SYN flooding
• Application-level attacks: HTTP request floods, expensive queries
• Reflection/amplification: DNS, NTP abuse using spoofed source IPs

Defensive Approaches

• Rate limiting and traffic filtering
• Load balancing and redundancy
• DDoS mitigation services and upstream filtering
• Monitoring and anomaly detection

Sniffing Attack

A sniffing attack involves capturing network traffic to observe sensitive information such as credentials, session tokens, or internal data. This attack is typically passive and difficult to detect.

Security Implications

• Plaintext protocols expose credentials directly.
• Session tokens can be reused to impersonate users.
• Internal network traffic is not inherently trusted.

Prevention

• Use encrypted protocols (HTTPS, SSH, TLS)
• Disable legacy plaintext services
• Apply switch security (ARP inspection, port security)
• Use VPNs on untrusted networks

Spoofing Attack

Spoofing attacks involve impersonating a trusted system or user by falsifying identity information at various network protocol layers.

Types

• IP spoofing
• ARP spoofing
• DNS spoofing
• Email spoofing

Defense

• Ingress/egress filtering
• ARP inspection and static mappings
• DNSSEC and secure resolvers
• Strong authentication over IP-based trust

Session Hijacking

Session hijacking occurs when an attacker takes control of an authenticated session by stealing or predicting session identifiers.

Common Methods

• Sniffing unencrypted session cookies
• XSS-based token theft
• Session fixation

Mitigation

• HTTPS enforcement
• Secure cookie attributes (HttpOnly, Secure)
• Session regeneration after login
• Timeouts and logout invalidation

Wireless Security

Wireless networks transmit data over radio signals, making them inherently more exposed than wired networks and easier to intercept.

Threats

• Eavesdropping
• Rogue access points
• Evil twin attacks
• Weak encryption exploitation

Best Practices

• Use WPA2/WPA3 encryption
• Separate guest and internal networks
• Disable open Wi-Fi
• Monitor for rogue APs