There’s a common concern among IT and security leaders: the fear of undetected hackers already lurking within their networks.
A recent study conducted by Hanover Research revealed that undetected security vulnerabilities top the list of concerns for networking professionals. The worry is well-founded—IBM’s 2024 Cost of a Data Breach Report shows it takes an average of 194 days to detect a breach.
High-profile ransomware attacks on companies like CDK and Synnovis underscore the damage stealthy hackers can inflict. The longer malicious actors operate unnoticed, the more proprietary and other information they can collect to hurt the company or fuel a larger attack.
To address this threat, it’s critical to recognize these five early warning signs:
1. Unusual account activity
Signs of unauthorized network access include unusual account activity, such as a spike in failed login attempts, which may indicate a brute force attack. Watch for users accessing unfamiliar applications or restricted areas, logins from unexpected locations or hours, and multiple simultaneous logins on a single account. Frequent account lockouts or an unusual surge in sent emails can also signal a breach.
2. Suspicious network traffic
Unusual network traffic can indicate a potential system breach. This may appear as sudden increases in network activity, particularly to or from unfamiliar sources or destinations, signifying an active attack or unauthorized data transfer. Communication with malicious botnets—especially with command-and-control servers—is another warning sign. Such abnormal amounts of DNS traffic might indicate the unauthorized transfer of data or secret communications. Unusual internal lateral movement, which suggests attackers seeking to spread across the network, is also a critical warning sign—as are network slowdowns or unexplained spikes in bandwidth usage.
3. System performance issues
Unexplained system performance issues–frequent application crashes or unusually high memory and CPU usage–can also indicate malicious activity. A sudden loss of access to critical resources may be a sign of attackers controlling or blocking access. Any unexpected pop-up windows or error notifications could also indicate active malware trying to disrupt operations or execute harmful actions.
4. Unauthorized changes in security settings
Unauthorized changes to security settings or audit logs may also be a sign of cybercriminals attempting to avoid detection. Attackers commonly change firewall settings to allow for malicious traffic or interfere with security tools. In some cases, they may disable or uninstall security software entirely. Even disabling notifications can delay responses from security teams, granting attackers additional time to exploit weaknesses without being noticed.
5. File and program changes
File and program changes—altered file locations, unusual file sizes, or the sudden disappearance of files—can be strong indicators of malicious activity. Suspicious file names or unexpected extensions that deviate from standard conventions should also raise immediate concern. Similarly, the appearance of new files or applications not installed by the user may point to a malware intrusion. Unauthorized changes to file or directory permissions could also signal attempts at privilege escalation or unauthorized access. Any surge in temporary files might indicate that malware may be running while attempting to avoid detection.
Speed Matters: Detecting and Stopping Hackers
Network security professionals must set up alerts for suspicious login activities, employ multi-factor authentication, and review user permissions. If a breach is suspected, deactivate it as quickly as possible. Change passwords and make certain that security protocols are followed to prevent additional breaches. Check all settings regularly.
You should also monitor your network closely for unexpected data transfers and traffic using uncommon ports or protocols such as SSH or remote desktop services that are not typically active. And always exercise caution with programs that unexpectedly seek access to the network.
Minimizing the length of time a silent attacker roams around a network is critical. While automated tools are great for catching threats faster, human expertise is still essential for recognizing the subtle anomalies that machines can miss. The most effective approach blends AI-powered analytics with skilled cybersecurity teams that can quickly assess and respond to threats.
Fast, effective incident response protocols are also essential. This includes regularly updating incident response plans and ensuring they are tailored to network-specific needs to reduce downtime and limit potential damage.
SD-WAN, SASE and MDR for Stronger Defense
With SD-WAN, security teams can monitor traffic patterns in real-time, making it easier to spot anomalies. Key advantages include:
- Better traffic segmentation: SD-WAN separates traffic between corporate resources, guest networks, and branch locations, minimizing the risk of cross-network attacks.
- Boosted network performance: By easing network congestion, organizations can reduce performance issues that hide malicious activity.
SASE takes this a step further by combining SD-WAN with advanced security tools like Zero Trust Network Access (ZTNA), Cloud Access Security Broker (CASB), and Firewall as a Service (FWaaS). This integrated approach enhances both connectivity and security. Key benefits include:
- Secure remote access: SASE applies security controls at the edge regardless of user location or device, ensuring safe connections for remote workers.
- Faster threat detection: With firewalls, intrusion detection/prevention, and behavioral analysis, SASE identifies and responds to threats quickly, reducing intruder dwell time.
- Cloud-native protection: For organizations using hybrid or multi-cloud environments, SASE secures data transfers and monitors for unusual activity across cloud services.
Managed Detection and Response (MDR) services are also available to provide continuous threat monitoring and rapid response to attacks that bypass traditional security controls. By integrating with SD-WAN and SASE, MDR enhances network resilience, detecting and mitigating threats in real time across endpoints, cloud environments, and operational technology. Combining automated analytics, third-party intelligence, and expert investigation, MDR reduces false positives, accelerates incident response, and gives organizations improved visibility into security events through detailed reporting.
Hackers can remain undetected for months, increasing the cost and impact of a breach. Firewalls and antivirus alone aren’t enough. A proactive defense—combining AI-driven security, expert monitoring, and a layered network strategy—is the best way to stay ahead of threats.
