How to identify hackers sitting in a computer network

Cybersecurity threats are an ever-present danger in today’s interconnected world, and one of the most insidious types of breaches involves hackers gaining access to a computer network and remaining undetected for long periods. These attackers, often referred to as “advanced persistent threats” (APTs), infiltrate networks, quietly lurking while they steal sensitive data, deploy malware, or cause other forms of damage. Identifying hackers who are sitting in your network is crucial to mitigating long-term harm and preventing data loss.

So, how can you identify these stealthy attackers? Here are some strategies and signs to look out for:

1. Monitor Unusual Network Traffic

Hackers typically require data exfiltration, and while they may try to keep things under the radar, unusual or unexplained network traffic is often a telltale sign. Keep an eye out for:

•    Outbound traffic spikes: This could indicate data being sent to an external server.
•    Unusual times of activity: If network activity peaks at odd hours (especially when most employees aren’t working), it could be an attacker operating quietly.
•    Communication with unknown external IPs: Look for communication with external IP addresses or domains that don’t belong to your company or have no legitimate purpose.

Tip: Use a Network Intrusion Detection System (NIDS) like Snort or Suricata to automatically flag suspicious traffic patterns.

2. Look for Unusual User Behavior

Hackers may attempt to blend in by impersonating legitimate users. However, there are always signs of abnormal behavior:

•    Unexplained login times: Logins at unusual times (like early mornings or weekends) might be a red flag, especially if they originate from locations outside the company’s usual operations.
•    Accessing restricted files: If employees or users are accessing files or systems they don’t typically interact with, this could indicate a hacker using legitimate credentials.
•    Multiple failed login attempts: A pattern of repeated failed login attempts, especially for privileged accounts, can signal an attempted brute-force attack.

Tip: Use User and Entity Behavior Analytics (UEBA) systems to detect out-of-the-norm behaviors based on historical data.

3. Check for New or Unauthorized Accounts

Hackers may create new accounts or escalate privileges to gain deeper access to your network. This can often fly under the radar, especially if they’re trying to maintain a low profile. Signs to watch for include:

•    New administrative accounts: Hackers may create unauthorized admin accounts to maintain long-term access to systems.
•    Changes to user permissions: If permissions or roles are altered without clear justification, it’s a red flag.
•    Increased privileged account activity: Accounts with elevated privileges (e.g., admin, superuser) being accessed unexpectedly.

Tip: Regularly audit user accounts and permissions, especially those with elevated privileges.

4. Examine Unexpected Software Installations

Hackers often install backdoors, rootkits, or remote access tools (RATs) on compromised systems to maintain persistent access. These may not always be detected by antivirus software, but there are other signs:

• New, unknown software running in the background: Software or processes that don’t belong to any authorized programs could be an indicator of malicious activity.

• Unexplained file or registry changes: Backdoors often make modifications to system files or the registry to enable persistent access.
• Outbound connections from unexpected applications: Tools like remote desktop software or terminal services may be used by hackers to control the system from afar.

Tip: Utilize endpoint detection and response (EDR) tools to keep track of unauthorized applications and monitor for unusual system behavior.

5. Check for System Slowdowns or Performance Issues

Although hackers prefer to stay undetected, their activities may cause disruptions in system performance. Watch out for:

•    Slower-than-usual system performance: If systems suddenly become sluggish, it could be a sign of malware running in the background.
•    High CPU or memory usage: Unexpected spikes in resource consumption can indicate a hacker running mining scripts, bots, or remote access tools.
•    Unusual disk activity: Excessive disk writing might indicate that hackers are exfiltrating data or spreading malware.

Tip: Use system monitoring tools like Nagios, Zabbix, or Prometheus to continuously monitor system health and performance metrics.

6. Investigate Failed or Suspicious Security Alerts

Hackers often try to bypass security measures or disable logging to avoid detection. Therefore, you should investigate:

•    Disabled antivirus or firewall alerts: If security measures like antivirus software or firewalls are disabled or tampered with, it’s a warning sign of a hacker’s attempt to make their activities undetectable.
•    Missing or altered logs: Attackers often delete or alter system logs to cover their tracks. Missing logs or inconsistent timestamps could indicate malicious activity.
•    Altered configuration files: Changes to security configurations, such as disabling logging or modifying firewall rules, should be reviewed closely.

Tip: Implement centralized logging and use Security Information and Event Management (SIEM) tools like Splunk or LogRhythm to detect suspicious log anomalies.

7. Perform Regular Vulnerability Scanning

Hackers often exploit known vulnerabilities in unpatched systems to gain access to a network. Regular vulnerability assessments can help you identify potential points of entry before an attacker does:

•    Outdated software or firmware: If critical systems are running outdated versions with known vulnerabilities, this could be a gateway for hackers.
•    Unpatched security flaws: Missing patches for operating systems, applications, or devices could provide an open door for cybercriminals.
•    Misconfigured systems: Weak configurations, such as open ports or weak passwords, can be exploited by attackers.

Tip: Use automated tools like Nessus or OpenVAS for vulnerability scanning, and implement a robust patch management system.

8. Utilize Threat Intelligence

In addition to monitoring your network, it’s helpful to stay informed about the latest cyber threats and hacker tactics:

• Threat feeds: Use threat intelligence feeds from trusted sources to stay updated on new vulnerabilities, hacker methodologies, and active attack campaigns.
• Collaboration with industry peers: Sharing threat intelligence with other organizations can help identify patterns of attack and improve your overall defense posture.

Tip: Platforms like ThreatConnect and Anomali can help organizations leverage threat intelligence in real-time to detect and mitigate hacker activities.

Conclusion

Identifying hackers sitting within a computer network requires a multi-layered approach that combines vigilant monitoring, regular audits, and proactive security measures. Hackers thrive on stealth, so the key to detecting them lies in consistently analyzing system behavior, user activity, and network traffic for anomalies. By using the right tools and strategies, IT professionals can increase the likelihood of detecting a breach before significant damage is done.

Remember, early detection is critical. The longer hackers remain in a network, the more damage they can inflict. Stay proactive and vigilant, and always be ready to respond at the first sign of trouble.