Identify and Eliminate Active Threats

Active threats can signal an immediate and ongoing attempt to compromise a network. They often involve attempts to initiate communication with IP addresses or ports that are not in use, a behavior that can indicate probing, misconfiguration, or even the early stages of an attack. This chapter explores active threats in detail, their implications, and effective strategies for investigation and mitigation.

What Is an Active Threat?

Definition: An active threat refers to any attempt to initiate a TCP connection to an IP address or port that is currently not in use. These connection attempts can signal probing activity or an effort to exploit network vulnerabilities. While not all active threats are inherently malicious, they should be scrutinized to ensure network integrity.

Examples of Active Threats:

• Unauthorized port scanning.
• Repeated attempts to connect to unused IP addresses.
• Attempts to communicate with closed or restricted services.

How Do Adversaries Exploit Active Threats?

Exploitation of active threats typically occurs in the early stages of an attack. Adversaries use these methods to:

• Map Network Vulnerabilities: Attackers attempt connections to various IPs and ports to identify potential entry points or unpatched services.
• Test for Misconfigurations: Probes help attackers find weaknesses, such as forgotten or improperly secured ports.
• Launch Exploitation Campaigns: Once an attacker finds an open, unused, or misconfigured endpoint, they may deploy payloads to compromise the target.

Example: An attacker might use automated tools such as Nmap or Masscan to scan a range of IPs and ports for services that can be exploited.

How Would Friendly Devices Become an Active Threat?

Friendly devices can sometimes behave like active threats due to misconfigurations or legitimate tasks:

• Misconfigured Services: Devices or applications that are improperly set up may attempt to reach unused or non-existent IP addresses or ports.
• Scheduled Scanning: Network security tools and vulnerability scanners might perform automated scans that trigger alerts as potential threats.
• Outdated Software: Legacy systems or old software versions may have configurations that cause them to behave unpredictably, attempting unnecessary connections.

Example: An internal monitoring tool configured with incorrect IP ranges might attempt to connect repeatedly to unused endpoints, appearing as an active threat to network monitoring systems.

How to Investigate an Active Threat

Proper investigation of active threats is essential to differentiate between benign activities and real threats:

• Log Analysis: Examine firewall and network logs to trace the origin of the suspicious connection attempts.
• Network Traffic Monitoring: Use tools such as Ridgeback to analyze the metadata of connection attempts and identify patterns that indicate malicious intent.
• Device Identification: Identify the source device or system initiating the connection to understand whether it’s a friendly device, a misconfiguration, or a potential intruder.

Best Practice: Ensure that threat investigation procedures are documented and that incident response teams are trained to recognize common signatures of active threats.

Repairing Misconfigurations

If an active threat is found to be caused by a legitimate device or system, take the following steps:

• Reconfigure Systems: Correct any network misconfigurations, such as incorrect IP ranges in scanning tools or services reaching out to obsolete endpoints.
• Patch and Update: Ensure that all systems are updated with the latest security patches to mitigate the risk of unexpected behaviors.
• Remove Redundant Services: Disable or remove any legacy services that are no longer required but may still be attempting connections.

How to Accommodate a Friendly Vulnerability Scanner

Friendly vulnerability scanners play an essential role in proactively identifying weaknesses, but they must be managed to avoid appearing as active threats:

• Define IP Ranges and Rules: Clearly define the IP ranges that the scanner can target and establish rules that prevent scans from probing outside approved network boundaries.
• Whitelist Devices: Configure network monitoring tools, such as Ridgeback, to recognize and accommodate scans from approved scanners without flagging them as threats.
• Schedule Scans: Conduct vulnerability scans during predefined maintenance windows to minimize the impact on network traffic and avoid false alarms.

How to Eliminate Active Threats

To effectively eliminate active threats from your network, consider the following measures:

A. Use Network Monitoring Tools

• Ridgeback: Employ Ridgeback to continuously monitor for suspicious connection attempts to unused IPs and ports. Its metadata analysis can detect and alert on these activities in real time.
• Intrusion Detection Systems (IDS): Deploy IDS tools to identify active threat patterns and raise alerts for deeper investigation.

B. Implement Network Access Controls

• Firewall Configurations: Strengthen firewall rules to block unauthorized connection attempts and log incidents for analysis.
• Access Lists: Use access control lists (ACLs) to restrict which devices or networks are allowed to communicate with specific parts of your network.
• Segmentation: Segment your network to limit the spread of any unauthorized connection attempts and contain potential threats.

C. Strengthen Device and Application Security

• Authentication and Authorization: Ensure all devices and applications authenticate before attempting connections.
• Regular Updates and Patching: Keep devices and software up to date to prevent vulnerabilities that may lead to active threat activity.
• Network Scanning: Use internal scanning tools to proactively identify open or unused ports and services that need to be closed or secured.

Conclusion

Identifying and eliminating active threats is essential to protecting your network from potential exploitation. By understanding the sources and motivations behind these connection attempts, whether friendly or malicious, network administrators can take informed action. Through diligent monitoring, timely investigation, and robust configuration, you can mitigate active threats and fortify your network’s security posture.