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How to spot data theft: 21 warning signs you should know (A practical guide)

Data theft is becoming increasingly easy, prompting IT professionals to remain vigilant for signs of data breaches. Data exfiltration is a growing issue affecting nearly every industry, including government sectors, educational institutions, and those utilizing roofing software or other specialized tools. With data moving at high speeds (at a rate of 10 gigabits per second), it can be quickly extracted.

It is essential to have a network protocol analyzer at critical entry and exit points operated by someone who can effectively trigger alarms under various conditions. There are excellent paid and open-source software options available to monitor and identify data leaks efficiently.

Where does the data go? Often to an IPv6 or IPv4 address, but not always. A Banana Pi M4, powered by a wall adapter and equipped with a 512GB flash card, can be easily removed just as it was installed. If it has a Wi-Fi data exit or another link to internal resources, it can lead to a significant data loss, both in terms of asset value and liability.

Cloud Access Security Brokers and data flow monitoring tools can help detect unusual activities. These solutions identify anomalies, but your real problem arises when you cannot spot these data outflows, underscoring the importance of automated penetration testing in securing your network.

Preventive measures are valuable, but no system is entirely foolproof due to the cleverness of malicious actors. It is important to stay alert for indications that something is wrong. Here are 21 indicators that your data might be compromised:

1. Detecting unfamiliar internal IP addresses or mismatched IP/MAC address pairs can indicate unauthorized devices on your network, suggesting a potential breach.

2. Sudden, large data transfers between internal hosts that do not typically communicate this way may signal data exfiltration attempts or compromised systems moving data covertly.

3. If your network has never used IPv6 but suddenly starts seeing traffic on this protocol, it could be a method for hidden data transfers, as IPv6 can bypass some older security measures.

4. Significant data flows to unfamiliar external IP addresses can indicate data is being sent to an unauthorized third party, which is a red flag for potential data theft.

5. Frequent changes in DHCP addresses, especially with new MAC addresses, can suggest a device is trying to avoid detection, which is a tactic often used by malicious actors.

6. The sudden appearance of new subnets or VLANs could mean that someone is creating hidden areas within your network for unauthorized activities, bypassing normal network controls.

7. If emails are suddenly larger than usual, it might indicate that sensitive data is being exfiltrated via email attachments, especially if organizational policies on email sizes are not well-defined.

8. Discovering multi-terabyte USB drives or other storage devices that violate your local storage policies can be a sign that someone is physically transferring large amounts of data out of your organization.

9. The appearance of new Wi-Fi hosts or access points not previously seen on your network can indicate unauthorized attempts to access or bridge into your network wirelessly.

10. Unusual patterns in browser uploads or unexpected traffic on VMware host ports can signify attempts to move data out of the network through web applications or virtual environments.

11. The sudden creation of new virtual machines can indicate misuse of local cloud resources, potentially for unauthorized tasks or data exfiltration.

12. The appearance of remote desktop applications like WinRM, RDP, or VNC can signify attempts to remotely access and control internal systems without authorization.

13. Finding unexpected traffic on ports used by FTP, SFTP, Telnet, and SSH can indicate unauthorized remote access or data transfer activities.

14. Consistently high data transfers nearing quota limits could suggest ongoing data exfiltration attempts designed to avoid detection by staying just under alert thresholds.

15. Using HTTP instead of the more secure HTTPS, or finding unencrypted data in packet traces, can expose sensitive information and indicate a security oversight.

16. Detecting NTLM network packets, which are often used by older, less secure NAS systems, can highlight vulnerabilities since NTLM is deprecated due to security risks.

17. Unauthorized changes to Access Control Lists (ACLs) for critical resources can indicate attempts to modify permissions to facilitate data theft or other malicious activities.

18. Discovering data sets that should have been deleted but remain or reappear can signal improper data management or attempts to keep sensitive data accessible.

19. In local, PaaS hosting, and other environments, accounts of departed employees that have not been removed or are being accessed can lead to unauthorized data access and potential breaches.

20. Unusually high levels of activity before scheduled audits can suggest covert data movement or other unauthorized activities intended to avoid detection.

21. Delays in updating or implementing new Privileged Access Management (PAM) credentials can leave systems vulnerable to unauthorized access.

Security professionals use numerous techniques to prevent data leaks, and the warning signs provided are just a starting point. This list serves as a helpful guideline, but generally, if something feels off, it likely is. Trust your instincts and stay vigilant.


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