What Is an Advanced Persistent Threat (APT)?

With the cybersecurity landscape changing more than ever, advanced persistent threats (APTs) are proving to be one of most important threats facing organizations.

APTs have changed the world of cybersecurity warfare. As these attacks become more frequent and complex, all sectors are potential targets. From agencies to businesses in the private sector, no one is immune: APTs are constant, behind-the-scenes threats.

This article will explore the key characteristics of APTs, how they operate, and, most importantly, outline essential strategies for prevention and defense.

What are advanced persistent threats?

Short for "advanced persistent threats", APT is a generalized term that refers to the processes and tools used by attackers who are sponsored by or associated with countries, organizations, or groups of individuals.

APTs are not the same as conventional cyber threats, and they distinguish themselves by being persistent in nature and targeted at specific entities or scopes. Generally, APTs are aimed at individual organizations or industries to gain access to sensitive data.

APT vs. ATP

Advanced threat protection (ATP) shouldn't be confused with APTs (advanced persistent threats).

• APT indicates the threat.
• ATP is a category of security solutions and technologies intended to address more advanced threats.

Characteristics of advanced persistent threats

APTs are some of the most sophisticated attacks. They have several characteristics that make them particularly damaging:

Long-term objectives and persistence

APTs are designed to achieve specific strategic goals over an extended period. Attackers are persistent and may remain undetected within a target network for months or years, continuously working toward their objective.

For example, Red Cross reported discovering an attack in January 2022 but believes the incident occurred months earlier in November 2021.

Highly skilled and well-funded threat actors

APTs are usually orchestrated by true threat actors: highly skilled individuals or groups with significant financial and technical resources, such as:

• Nation-states
• Organized crime groups
• State-sponsored hacking groups

Sophisticated techniques and tools

Malicious actors employ advanced methods to infiltrate and compromise their targets, like:

• Zero-day exploits
• Custom malware
• Social engineering
• Spear-phishing

They may also use encrypted communication channels and other tactics to avoid detection.

Targeted at specific organizations or industries

APTs are highly targeted attacks aimed at specific organizations, industries, or governments with valuable information or assets. Attackers carefully select their targets based on the potential strategic value.

Masters of stealth

A key characteristic of APTs is their focus on remaining undetected within the target’s network. Attackers employ various tactics to maintain a low profile, such as

• Using legitimate credentials.
• Blending in with regular network traffic.
• Erasing traces of their activities.

Leveraging multi-stage attacks

APT attacks typically involve multiple stages — such as reconnaissance, exploitation, establishing a foothold, lateral movement, and data exfiltration or disruption of operations. (If these sound similar to the cyber kill chain, you're not wrong.) Each stage is carefully planned and executed to maximize the chances of success and minimize the risk of detection.

Now let’s turn to these individual stages.

How attackers execute APTs

APT attacks are complex and require significant skill and resources to be executed successfully. Understanding each stage of an APT attack could help your organization develop robust defense strategies and effectively mitigate the risk posed by them.

Reconnaissance

Before launching an attack, malicious attackers take time to gain information about their target. They’ll study the organizational structure, employee profiles, network infrastructure, and potential vulnerabilities. To get critical information, they leverage:

• Open-source intelligence (OSINT) 
• Social engineering
• Network scanning

Initial compromise and gaining access

Once they’ve done their homework and have sufficient information, attackers choose an entry point into the target’s network. This may involve exploiting vulnerabilities, spear phishing, or using stolen or compromised credentials. The attackers may use custom malware or zero-day exploits to bypass robust security measures.

Attackers often create other cyber threats as a smoke screen to throw security professionals off their trail. For example, they may execute a DDoS attack, which also weakens the security perimeter.

Establishing a foothold and persistence

After gaining initial access, the attackers establish a foothold in the target network. They’ll often install malware, such as backdoors or rootkits. This allows them to keep access to the network and operate undetected, even if their initial entry point is discovered and closed.

(Related reading: malware & malware detection.)

Privilege escalation

Once they have an established, persistent presence in the target’s network, the attackers will work to escalate their privileges within it. They often exploit vulnerabilities in the target’s systems or leverage stolen credentials. By doing so, they gain administrative control over critical assets and systems.

Lateral movement within the network

With higher privileges, malicious actors move laterally within the network, compromising even more systems and accounts. They may use tools like pass-the-hash or pass-the-ticket to access other network parts and gather more information or assets.

(Learn how to use Splunk to detect lateral movement.)

Data exfiltration and disruption

Once the attackers have achieved their objectives, such as stealing sensitive data or intellectual property, they carefully exfiltrate the data from the target’s network. Sometimes, they may disrupt operations or deploy ransomware to cause more damage or obfuscate their activities.

(Related reading: ransomware trends.)

Maintaining stealth and avoiding detection

Throughout the entire process, staying undetected is the attacker’s primary goal. They do this through many different tactics, including

• Leveraging legitimate credentials
• Blending in with regular network traffic
• Clearing all traces of their activities

Sometimes, they maintain access and monitor the target’s network even after achieving their primary objectives.

Exit strategy

Once they’ve achieved their objectives or believe they’re at risk of being caught, many attackers initiate a planned exit strategy. This involves:

• Erasing their activities. 
• Removing backdoors or malware. 
• Ensuring they leave no evidence that could lead to their identification.

Defending against APTs

Organizations must adopt a comprehensive and proactive approach to cybersecurity to defend against APT attacks. Let's review some strategies.

Develop a robust cyber security framework

Implement a strong cybersecurity framework based on recognized standards, such as:

• The  NIST Cybersecurity Framework 
• ISO/IEC 27001

This should include processes for risk management, asset identification, and vulnerability management.

Train employees and increase awareness

Attackers often leverage employees to get into sophisticated systems. Conduct regular security awareness training to help employees recognize and respond to phishing attempts, social engineering attacks, and other threats.

Segment the network & implement access control

• Segment the network to limit the movement of an attacker in case of a breach.
• Implement strict access controls, including the principle of least privilege, to ensure users and systems have access only to the information necessary to perform their duties.

Stay up to date on threat intelligence and information sharing

Stay current on emerging threats, vulnerabilities, and attack techniques by reading threat intelligence feeds and participating in information-sharing initiatives. Collaborate with other organizations, industry groups, and government agencies to stay ahead and informed of evolving APT threats. Follow SURGe and Splunk Threat Research Team for the latest intel and brand-new and long-term strategies for defense.

(Related reading: what are ISACs?)

Conduct regular security audits and assessments

Conduct regular security audits, vulnerability assessments, and penetration testing to find and fix network and application weaknesses. Proactive defenses are critical to addressing vulnerabilities before APT attackers can take advantage of them.

Maintain incident response and recovery plans

Develop and maintain a comprehensive incident response plan that includes procedures for detecting, containing, and remediating APT attacks. Regularly review and update the plan to ensure it remains effective and relevant in the face of evolving threats.

Protect with multi-factor authentication and encryption

Secure important systems, applications, and use cases by implementing multi-factor authentication (MFA) in order to decrease the risk of unauthorized access. Sensitive data should be encrypted both in transit and at rest with strong encryption algorithms as well by secure key management practices. Enforce strong access controls using the principle of least privilege.

Monitor for APTs

APT discovery includes:

• Having strong monitoring in place to detect abnormal network behaviors.
• Leveraging SIEM systems for log analysis.
• Building robust endpoint protection system solutions. 

AI and machine learning algorithms can be used alongside regular threat hunting exercises to find hidden security threats. Organizations should also make use of threat intelligence feeds to remain abreast of what is happening in the wild, thus improving their detection capabilities around APT tactics.

(Related reading: security monitoring.)

NIST and APTs

The National Institute of Standards and Technology (NIST) establishes a series of guidelines and frameworks that enable organizations to refine how they view the risks associated with APTs.

NIST SP 800-30 Rev 1

NIST SP 800-30 Rev 1 provides a structured approach to risk assessments, which is crucial in order to both identify and manage the risks associated with APTs. This publication outlines the significance of knowing about the threat landscape, vulnerability assessment, and what threats may impact organization operations. These guidelines can be used by organizations to develop a complete risk assessment sequence for the identifying and classifying specific APTs and designing corresponding defenses.

NIST SP 800-39

NIST SP 800-39 provides a complete view of how to manage information security risk in an organization. This illustrates the necessity of a contextualized risk management framework for which threat assessment should be performed at both business and technical levels.

APTs: The silent, stealthy danger in our digital world

APTs pose a significant challenge to organizations and governments worldwide. Their targeted, stealthy, and sophisticated nature make them more harmful than most cyberattacks. As the digital landscape continues to evolve, APT attackers are becoming more adept at infiltrating networks, remaining undetected, and achieving their objectives.

Organizations must adopt proactive and multi-layered approaches to cybersecurity defenses to reduce threats effectively. Robust security frameworks, employee awareness, and collaboration are essential to building a resilient defense against APTs. As the threat landscape shifts, it takes a commitment to continuous improvement, collaboration, and cyber resilience to stay one step ahead of these formidable adversaries and safeguard our world.