212-89 Network Level Incidents

Network Level Incidents Detailed Explanation

Network-level incidents refer to attacks that target the network infrastructure, aiming to disrupt, eavesdrop, or gain unauthorized access to network resources. Common examples include DDoS (Distributed Denial of Service) attacks, session hijacking, and network scanning. These incidents can result in service downtime, data theft, or network compromise.

Network-level incidents are often more complex and can impact multiple devices across the network. The incident response team must act quickly to detect, contain, and resolve these incidents to minimize damage. Let’s go through each key step involved in handling network-level incidents.

Key Steps to Handling Network Level Incidents:

1. Monitor and Detect Anomalous Traffic
2. Analyze Attack Patterns
3. Implement Defensive and Containment Measures
4. Clear and Restore Normal Network State

1. Monitor and Detect Anomalous Traffic

The first step in handling network-level incidents is to continuously monitor network traffic to detect unusual or suspicious activities. Early detection is essential for preventing incidents from escalating and affecting more of the network.

• Using IDS (Intrusion Detection Systems):

  • An IDS is a network security tool that monitors traffic for suspicious patterns and sends alerts if it detects any signs of attack.
  • IDS tools analyze data packets, looking for specific attack signatures (patterns of malicious activity) or unusual traffic patterns.
  • There are two main types of IDS:
    • Signature-based IDS: Detects attacks by comparing traffic against a database of known attack signatures.
    • Anomaly-based IDS: Establishes a baseline of normal network activity and detects deviations from this baseline as potential threats.
  • Popular IDS tools include Snort and Suricata, which are widely used for real-time traffic monitoring and threat detection.

• Traffic Analysis Tools:

  • NetFlow: NetFlow is a tool that analyzes network traffic by tracking IP flows, or streams of data between devices, which can reveal bandwidth usage and highlight unusual data transfers.
  • Wireshark: Wireshark is a packet capture tool that allows detailed inspection of individual data packets, including their contents, source, and destination. It’s particularly useful for spotting specific malicious activities, such as unauthorized data transmission.
  • Analyzing Network Traffic: The goal is to detect anomalies, such as unusually high data volume (indicative of DDoS), connections to unfamiliar IPs (potential signs of session hijacking), or repetitive port scanning (signs of network scanning by attackers).

By regularly monitoring network traffic, the team can spot potential threats early and take immediate action to investigate them further.

2. Analyze Attack Patterns

Once suspicious traffic is detected, the next step is to analyze the attack patterns to identify the type of incident and its source. This helps the team understand the attacker’s tactics and enables a more targeted response.

• Traffic and Log Analysis:

  • Traffic analysis involves inspecting the characteristics of data packets to determine if they match known attack behaviors.
  • Log Analysis: Network devices like routers, firewalls, and servers keep logs of all incoming and outgoing traffic, including timestamps, IP addresses, and data transfer details.
  • By analyzing these logs, the team can trace the origin and path of the suspicious traffic and understand the attack’s scale and direction.

• Identifying Attack Types:

  • Different network-level attacks have distinct characteristics, so identifying the type of attack can help narrow down the source and the best response.
    • DDoS (Distributed Denial of Service): A DDoS attack floods the network with excessive traffic to overwhelm the system, often causing slowdowns or outages. In logs, DDoS attacks appear as an abnormally high volume of traffic from multiple IP addresses.
    • Session Hijacking: This attack involves intercepting and taking control of a user’s session with a service. Signs of session hijacking include unauthorized requests from a user’s IP or suspiciously timed session data.
    • Network Scanning: Scanning attacks are typically reconnaissance attempts to identify open ports or services. They appear in logs as repetitive connection attempts across multiple ports or IP addresses.
    • Sniffing (Packet Capture): Sniffing is eavesdropping on network traffic to capture sensitive data like passwords or personal information. It may not always leave obvious traces in logs, but it can be detected by monitoring for unauthorized devices on the network.

Analyzing attack patterns allows the team to respond effectively and determine which systems or devices need immediate action.

3. Implement Defensive and Containment Measures

Once the attack type is identified, it’s essential to contain the attack and strengthen defenses to prevent further damage.

• Adjusting Firewall Rules:

  • Firewalls control incoming and outgoing network traffic. Adjusting firewall rules can block traffic from suspicious IPs or restrict access to specific services, mitigating the effects of an attack.
  • For example, in response to a DDoS attack, firewall rules can be set to limit traffic rates from each IP, or even temporarily block specific geographic locations if the attack is coming from a particular region.

• Applying Access Control Lists (ACLs):

  • ACLs are a set of rules that define what traffic is allowed or denied access to the network. By applying ACLs, the team can block specific IP addresses, restrict access to certain ports, or limit the types of traffic allowed on the network.
  • ACLs are particularly useful for restricting access to network services and isolating specific network segments, which can contain threats and prevent them from spreading.

• Modifying Intrusion Prevention System (IPS) Settings:

  • IPS actively monitors traffic for signs of attack and blocks or contains malicious activity in real time.
  • IPS settings can be modified to trigger a response if specific attack signatures are detected, such as blocking connections from IPs that attempt unauthorized access repeatedly.
  • For example, if an IPS detects repeated login attempts from an IP, it can block further attempts from that IP to prevent a brute-force or session hijacking attack.

By implementing these defensive measures, the team can control and contain the attack, minimizing its impact on the network and preventing it from escalating.

4. Clear and Restore Normal Network State

Once the attack has been contained and blocked, it’s time to clear the network of any lingering effects of the attack and restore normal operations.

• Clearing Infected or Affected Devices:

  • If any devices were compromised during the attack, it’s crucial to inspect and clean them before reconnecting them to the network.
  • Anti-malware scans should be run on affected devices to ensure no malicious software remains.
  • The team should also check for any suspicious changes made to the device settings or configurations, such as unauthorized firewall rule changes.

• Updating Router and Switch Configurations:

  • Attackers may alter router or switch settings to facilitate further attacks. As a preventive measure, review and update device configurations.
  • Change Passwords: If the network device credentials may have been exposed, update them with stronger, unique passwords.
  • Apply Firmware Updates: Firmware updates often contain security patches that can protect devices from known vulnerabilities.
  • Recheck firewall and ACL configurations to confirm they’re correctly set to prevent further access from malicious sources.

• Restoring Normal Traffic Flow:

  • After clearing the network, remove any temporary containment rules that were applied, such as IP blocks, traffic rate limits, or geographic restrictions, unless they are necessary to protect against future incidents.
  • Monitor traffic for any residual signs of the attack to confirm that all malicious activity has ceased and normal traffic flow has resumed.

Clearing and restoring the network ensures that all malicious influences are removed, and regular operations can continue without interference. Additionally, this step helps prevent any further disruptions by making sure the network is secure.

Summary of Handling Network Level Incidents

Handling network-level incidents involves several key steps: detecting and monitoring traffic, analyzing attack patterns, implementing defensive and containment measures, and clearing the network to restore normal operations. Each step helps ensure that network attacks are quickly detected, effectively managed, and fully resolved, minimizing their impact on the organization. By following these steps, incident response teams can maintain a secure network environment and be better prepared for any future network-level threats.

Network Level Incidents (Additional Content)

1. Lateral Movement & Network Persistence

Why Is It Important?

• Advanced Persistent Threats (APT) do not rely on a single-entry point—instead, attackers aim to move laterally within the internal network to escalate privileges and gain broader control.
• Standard firewalls and intrusion detection systems (IDS/IPS) mainly focus on north-south traffic (incoming/outgoing traffic), but APTs often operate internally using east-west traffic (lateral movement).
• Attackers use Pass-the-Hash (PTH), Remote Code Execution (RCE), and stolen credentials to access more sensitive resources.

Suggested Additions

1. East-West Traffic Monitoring for Lateral Movement Detection

Lateral movement is difficult to detect using traditional north-south monitoring. Instead, organizations must deploy internal network traffic analysis (NTA) solutions.

Detection Method	Implementation	Purpose
Network Traffic Analysis (NTA)	Use Cisco Stealthwatch, Zeek (Bro IDS), Darktrace	Detect internal anomalous communications between servers.
East-West Flow Visibility	Deploy flow-based analysis (NetFlow, sFlow, IPFIX)	Identify unusual communication between non-related devices.
Lateral Traffic Anomaly Alerts	Set up alerts for excessive internal traffic, SMB enumeration, and repeated authentication attempts	Flag attempts to access multiple internal servers suspiciously.

Example Use Case:
An attacker gains initial access via a compromised employee’s laptop and starts probing the network for other accessible devices. Network behavior analysis detects unusual SMB authentication attempts to multiple servers and triggers an alert, leading to immediate containment of the compromised machine.

2. Detecting Abnormal Authentication & Privilege Escalation

Threat actors often use stolen credentials and remote management tools to escalate their privileges.

Indicator	Detection Method	Example Attack
Abnormal RDP Usage	Monitor RDP login attempts from unauthorized workstations	Attackers use Remote Desktop Protocol (RDP) for lateral movement.
PsExec/WMI Execution	Detect use of remote execution tools (PsExec, WMI, PowerShell Remoting)	A compromised device executes commands on another machine without user interaction.
Unusual Account Privilege Changes	Log sudden privilege escalations (user → admin)	An attacker converts a standard user into a privileged administrator to expand access.

Example Use Case:
A low-privilege account is suddenly granted Domain Admin access, triggering an automatic SIEM alert. Security teams immediately investigate and discover that the account was compromised and used to move laterally across the environment.

3. Network Segmentation to Prevent Lateral Movement

Even if an attacker gains initial access, network segmentation can prevent them from moving freely.

Segmentation Strategy	Implementation	Objective
VLAN Segmentation	Assign critical assets (databases, admin systems) to separate VLANs	Prevent infected workstations from accessing privileged systems.
Microsegmentation (Zero Trust)	Use host-based firewalls and security policies per device	Limit which devices can communicate with each other.
Strict Access Control Lists (ACLs)	Define granular access rules for east-west traffic	Ensure only authorized systems can communicate with each other.

Example Use Case:
A hospital's medical devices are isolated in a dedicated VLAN, ensuring that even if a workstation is infected with ransomware, the attack cannot reach critical patient monitoring systems.

2. Zero-Day Network Exploits & Encrypted Traffic Analysis

Why Is It Important?

• Traditional firewalls and IDS/IPS rely on known attack signatures, but zero-day exploits allow attackers to bypass traditional defenses.
• More than 80% of global internet traffic is now encrypted (TLS 1.3, DoH - DNS over HTTPS), making it harder to inspect for threats.
• Attackers use encrypted command-and-control (C2) traffic, DNS tunneling, and fake SSL certificates to hide malicious activity.

Suggested Additions

1. Behavioral Analytics for Zero-Day Exploit Detection

Instead of relying solely on signatures, User and Entity Behavior Analytics (UEBA) can detect unusual network behavior.

Behavioral Threat Indicator	Detection Method	Example Attack
DNS Tunneling (Data Exfiltration)	Detect excessive DNS queries to unknown domains	Malware sends stolen data via DNS lookups instead of HTTP requests.
TLS Fingerprint Anomalies	Identify use of self-signed or unknown SSL certificates	Attackers use custom TLS settings to evade detection.
Unusual Traffic Patterns	Monitor unexpected data transfers between unrelated hosts	Zero-day malware spreads across internal networks via SMB without external access.

Example Use Case:
A finance server starts making frequent encrypted connections to an unknown external IP. Behavioral analytics detects this deviation from normal traffic patterns and flags it as potential malware communication.

2. Encrypted Traffic Analysis (ETA) Without Decryption

Since TLS 1.3 prevents deep packet inspection, security teams must analyze encrypted traffic without decryption.

ETA Technique	Implementation	Purpose
TLS SNI (Server Name Indication) Monitoring	Analyze destination domains in encrypted sessions	Detect access to known malicious servers.
Packet Metadata Analysis	Track session lengths, data volume, frequency	Identify C2 traffic disguised as normal encrypted web traffic.
Encrypted Flow Fingerprinting	Use AI to compare traffic patterns with known malware activity	Detect malware communicating over encrypted channels.

Example Use Case:
A corporate laptop connects to a suspicious domain via TLS 1.3. Even though the payload is encrypted, the security system detects that the handshake pattern matches a known malware family, triggering an immediate investigation.

3. Threat Intelligence Feeds for Zero-Day Network Defense

Organizations should subscribe to real-time threat intelligence feeds to stay ahead of newly discovered exploits.

Threat Intelligence Source	Use Case
AlienVault OTX	Provides crowdsourced zero-day IoCs.
IBM X-Force Exchange	Tracks threat groups and their tactics.
VirusTotal Threat Intelligence	Scans for new malicious domains and IPs.

Example Use Case:
A security team integrates threat intelligence feeds into their SIEM, allowing automatic blocking of newly discovered zero-day exploit domains before they can be used in an attack.

Final Summary: Key Enhancements to Network Level Incidents Response

Aspect	Enhancement
Lateral Movement & Network Persistence	Use east-west traffic monitoring, abnormal authentication detection, and strict network segmentation to prevent attackers from spreading internally.
Zero-Day Exploits & Encrypted Threat Analysis	Implement behavioral analytics, AI-driven encrypted traffic analysis, and real-time threat intelligence feeds to detect and mitigate advanced network threats.