How can you effectively test your security against advanced persistent threats (APTs)?

Spend time to determine who your key known threat actors are. Mitre ATT&K is a good starting point, they list known threat actors and cover their known TTPs. After narrowing down who would attack you, and why. Consider what they might try to take or access? Locate all the key systems in your company that hold things of value that the threat actors might come for. Take the Attack TTPs and prioritise building detections for those TTPs on the critical systems. Implement a purple teaming/attack simulation tool to test your detections. Run a paper-based exercise to test IR processes. After you have done these steps engage a red team or pen testing firm to help validate everything. Make sure to use a continuous cycle of test/improve.

Identify valuable assets: Data, systems, and processes critical to your business. Understand potential threats: Adversaries, motives, and common APT tactics. Evaluate current security controls: Gaps and vulnerabilities in your defenses.

Employ a combination of penetration testing, threat intelligence analysis, and red team exercises. Implementing robust endpoint detection and response (EDR) systems and network traffic monitoring aids in detecting APT activities. Conducting simulated APT attacks can uncover vulnerabilities and assess the organization's readiness. Regular security assessments and audits help identify weaknesses for remediation. Utilizing sandbox environments for testing potential APT scenarios enhances preparedness. Continuous security awareness training for employees mitigates the human factor in APT attacks. Lastly, collaborating with industry peers and sharing threat intelligence enhances collective defense against APTs.

Scan all assets: Regularly assess internal & external systems for weaknesses. Use diverse tools: Combine automated scanners with manual penetration testing. Prioritize critical vulnerabilities: Address high-risk issues promptly.

If you can afford it engaging with a security testing company that can run a "proper" red teaming activity can be a great way to find issues. This engagement should be run over multiple months, with a number of high value targets. It should be somewhat open scope, allowing the attacking team to use any means at their disposal to find a way in. I personally feel that phishing and attacking people is somewhat a waste of money for an exercise like this, at least in the early stages. Perhaps focus on perimeter assets, if the company is skilled enough, they should be able to develop exploits for systems, or leverage configuration issues, or break into a building to find an initial foothold. Ramp up the noise over the next weeks until caught.

Simulate real-world attacks: Mimic APT tactics like social engineering and phishing. Target high-value assets: Focus on systems with sensitive data or critical processes. Engage skilled professionals: Hire experienced penetration testers or red teams.

Gather APT intel: Track adversary tactics, techniques, and indicators of compromise (IOCs). Analyze data: Identify potential threats and adjust security controls accordingly. Share threat intel: Collaborate with industry partners to stay informed.

Network and Security admins typically underestimate the value of 24x7 monitoring of network activities and logs. For example, a breached PC might show an added PORT, or a new service. This happens when the hackers install RATs or reverse shells. Without monitoring, these malicious activity could go undetected for a longer period of time. The hacker would do more damage in the intervening time.

1. Assess Risk Profile: Identify critical data & systems. Understand potential attackers & tactics. Evaluate current security controls. 2. Vulnerability Scanning: Regularly scan internal & external systems. Combine automated & manual testing. Prioritize critical vulnerabilities. 3. Penetration Testing: Simulate real-world APT attacks. Target high-value assets with sensitive data. Engage skilled penetration testers. 4. Threat Intelligence: Track adversary tactics & indicators. Analyze data to adjust security controls. Share threat intel for industry collaboration. 5. Review & Improve: Regularly assess test results & security posture. Update controls & remediate vulnerabilities. Continuously improve security posture.

Consider monitoring DNS client queries as well. DNS to DGA domains could be a sign of infection. This usually means the infected PC is trying to connect to Command and Control servers. Secondly, DNS with a lot of TXT going OUT could be a sign of data exfiltration. Hackers are known to use DNS txt as a means of sending data packets out of the network. Why? because DNS ports are typically open. Finally DNS client queries to non-work related sites could be a sign that the user is non productive. The user with the most number of DNS queries would warrant a closer inspection.

A combination of all the above and more would be a good strategy to test your defenses against APTs. One of my favorites is verifying effectiveness of your network segmentation strategy. Network segmentation is dividing your network into smaller sub-networks.