Best Practices for Monitoring Suspicious Network Activity

Monitoring suspicious network activity is one of the most critical tasks in maintaining the security and integrity of any organization’s IT infrastructure. With the increasing frequency and sophistication of cyberattacks, a proactive approach to identifying and mitigating threats is essential. Threat actors are constantly evolving their tactics, making it crucial for organizations to deploy robust network monitoring practices that can detect unusual behavior before it escalates into a full-blown security incident.

This blog will outline best practices for monitoring suspicious network activity, covering key areas such as tools and technologies, effective strategies, and common indicators of compromise (IoCs) that IT security teams should be aware of.

Why Monitoring Suspicious Network Activity is Important

The primary objective of network monitoring is to detect, respond to, and prevent cyberattacks that can compromise data, disrupt operations, or damage your organization’s reputation. By closely monitoring network traffic, organizations can identify:
– Unusual patterns or spikes in traffic that might indicate an ongoing cyberattack.
– Unauthorized access attempts or breaches of critical systems.
– Data exfiltration attempts where sensitive information is being transferred out of the organization.
– Malware spreading across the network.

By detecting these signs early, security teams can contain threats and minimize damage before attackers gain a foothold in the system.

Best Practices for Monitoring Suspicious Network Activity

1. Use Comprehensive Monitoring Tools

To effectively monitor network activity, you need a suite of tools that can collect, analyze, and alert you to potential threats in real-time. Some essential monitoring tools include:

– Intrusion Detection and Prevention Systems (IDPS): These tools detect and block suspicious activities or known attack patterns. They can be deployed at the network perimeter or within the network to monitor traffic.
– Security Information and Event Management (SIEM) Systems: SIEM solutions aggregate log data from various sources, correlate it, and generate alerts based on predefined rules. This allows for centralized monitoring and helps identify patterns that might indicate a threat.
– Network Traffic Analysis (NTA) Tools: These tools monitor network traffic in real-time and provide visibility into the flow of data across the network. NTA tools can detect anomalies, such as large file transfers, that might indicate data exfiltration.
– Endpoint Detection and Response (EDR) Tools: EDR tools monitor activities on endpoints (such as workstations and servers) to detect signs of malware, unauthorized access, or unusual user behavior.
– Firewall and VPN Logs: Regularly reviewing logs from firewalls and VPNs can reveal unauthorized access attempts or unusual traffic coming from external sources.

Using a combination of these tools ensures you have a comprehensive view of network activity and can detect both known and unknown threats.

2. Establish a Baseline for Normal Network Activity

One of the key strategies for identifying suspicious network activity is knowing what “normal” looks like. By establishing a baseline for typical network behavior, you can quickly spot anomalies that deviate from the norm.

Key metrics to track when establishing a baseline include:
– Average network bandwidth usage: Monitor how much data is typically transmitted across your network during various times of the day and week.
– Commonly accessed systems: Identify the systems, servers, and applications that are frequently accessed by employees or systems.
– User behavior: Track normal user activity, including logins, file access, and data transfers. Look for anomalies like employees accessing sensitive data at odd hours or transferring large volumes of data unexpectedly.
– Traffic patterns: Map out which IP addresses, domains, and external services your network regularly interacts with.

Once a baseline is established, any deviation from this normal activity can trigger an alert, signaling a potential security threat.

3. Implement Real-Time Alerts for Anomalous Activity

To react swiftly to potential security incidents, real-time alerting is essential. Modern monitoring tools allow for the creation of customized alerts based on specific triggers, including:

– Unusual login activity: Multiple failed login attempts or logins from unusual geographic locations can indicate a brute force attack or compromised credentials.
– Abnormal data transfer rates: Large file transfers or unusual volumes of outbound traffic can signal data exfiltration attempts.
– Unauthorized access: If a user accesses sensitive data or systems outside their usual scope of responsibility, it could indicate an insider threat or a compromised account.
– Malware signatures: Detect known malware signatures or behaviors that can indicate an ongoing infection.
– Suspicious internal traffic: Detect lateral movement across the network, where attackers try to move from one compromised system to others in the network.

Set up alerts to notify security personnel via multiple channels (e.g., email, SMS, or integrated incident response platforms) to ensure swift action is taken when an anomaly is detected.

4. Enable Continuous Network Traffic Monitoring

Continuous monitoring is essential for identifying subtle or persistent threats that might evade detection if you rely on periodic scans. Cyberattacks often involve months of reconnaissance and subtle probing before the final attack occurs. Without continuous monitoring, these early warning signs can be missed.

To achieve effective continuous monitoring, organizations can:
– Deploy network sensors across different parts of the infrastructure to capture and analyze traffic in real-time.
– Monitor critical assets closely, such as database servers, financial systems, and sensitive data repositories.
– Track endpoint behavior to identify malicious activity on devices like laptops, desktops, and mobile devices that connect to the network.
– Leverage threat intelligence feeds to keep the monitoring system updated with information on the latest vulnerabilities, attack techniques, and indicators of compromise (IoCs).

Continuous monitoring reduces the time an attacker can operate undetected and minimizes the risk of a prolonged breach.

5. Monitor User Behavior with User and Entity Behavior Analytics (UEBA)

User and Entity Behavior Analytics (UEBA) tools use machine learning to analyze user behavior and detect anomalies that indicate potential insider threats, compromised accounts, or malicious activities. These tools help identify suspicious actions, such as:

– Abnormal login times or locations: A user logging in at unusual hours or from an unusual IP address could be a red flag.
– Unusual access patterns: A user suddenly accessing files or systems they don’t typically use may indicate suspicious behavior.
– Multiple failed login attempts: Brute force attacks often involve repeated failed attempts to guess a password.
– Unusual file movements or downloads: A sudden spike in file access or large data transfers may signal an insider threat or data exfiltration.

By applying machine learning algorithms, UEBA systems can spot subtle deviations from normal user behavior and provide early warnings before significant damage occurs.

6. Track Network Flows to Detect Anomalies

Monitoring network flows (NetFlow or IPFIX data) provides visibility into the volume, source, and destination of traffic flowing through your network. This type of monitoring helps identify suspicious patterns, such as:

– Communication with known malicious IPs: An internal system communicating with a known Command-and-Control (C2) server could indicate a compromised system.
– Unusual inbound or outbound traffic spikes: A sudden increase in traffic volume, especially outbound traffic, may signal a Distributed Denial of Service (DDoS) attack or data exfiltration.
– Geographic anomalies: Network traffic originating from or directed to unexpected geographic regions might indicate an attack from foreign threat actors.

By tracking network flows, security teams can get a high-level view of traffic trends and zoom in on potential threats before they cause significant harm.

7. Perform Regular Log Audits

Logs from firewalls, servers, routers, VPNs, and endpoints are a goldmine of information when it comes to detecting suspicious network activity. Conducting regular log audits helps identify:

– Repeated failed login attempts or account lockouts, which may indicate brute force or credential stuffing attacks.
– Unauthorized access to sensitive data or systems outside of normal business hours.
– Changes in system configurations or permissions, which could indicate tampering or unauthorized access.

While real-time monitoring is essential, conducting regular log audits helps uncover incidents that might not have triggered immediate alerts but still pose a security risk.

8. Segment Networks and Monitor Internal Traffic

Implementing network segmentation ensures that different parts of your infrastructure are isolated from one another, limiting the ability of an attacker to move laterally within your network if one system is compromised.

Once the network is segmented:
– Monitor traffic between segments: Look for unusual communication between isolated systems or networks that should not interact with each other.
– Inspect internal traffic: Not all threats come from the outside; internal actors, whether malicious insiders or compromised accounts, can also pose a significant risk. Monitoring internal traffic can help detect lateral movement by attackers attempting to explore and compromise other systems.

Network segmentation also helps contain incidents, making it harder for attackers to spread malware or exfiltrate data from multiple systems.

9. Automate Incident Response with SOAR

Security Orchestration, Automation, and Response (SOAR) platforms integrate with your monitoring tools to automate responses to suspicious activities. By predefining responses to specific alerts, SOAR tools can:

– Automatically block malicious IPs or domains.
– Isolate compromised systems from the network.
– Trigger incident response playbooks for handling specific types of threats.
– Coordinate actions across multiple tools to ensure a swift and cohesive response to incidents.

SOAR platforms help reduce the response time and free up security analysts to focus on more complex investigations.

Common Indicators of Suspicious Network Activity

When monitoring network activity, look for these key Indicators of Compromise (IoCs) that often signal suspicious or malicious behavior:

– Unexplained network traffic spikes: Sudden and significant increases in data flow, especially during non-business hours, may indicate malicious activity.
– Failed login attempts:A large number of failed login attempts, especially from unknown IPs, can be an early sign of brute force attacks.
– Unusual outbound traffic: A compromised system may attempt to send large amounts of data outside the network to a malicious server.
– New devices on the network: An unexpected device connecting to the network can indicate an attacker’s attempt to gain access.
– Abnormal process behavior: Malware often executes unusual or unexpected processes on compromised systems, which can be detected through monitoring.

Conclusion

Effectively monitoring suspicious network activity is essential for protecting your organization against the constant threat of cyberattacks. By implementing comprehensive tools, establishing baselines, enabling real-time alerts, and leveraging advanced analytics, you can detect and respond to potential threats before they escalate into major security incidents. Continuous monitoring, combined with automated incident response capabilities, ensures your organization stays ahead of attackers and minimizes the damage from security breaches.

By following these best practices, your security team will be better equipped to safeguard your network, data, and systems from malicious actors.