What is an APT (Advanced Persistent Threat)?

Advanced Persistent Threats (APTs) can wreak havoc by side-stepping security defenses and evading detection for months. The increasingly sophisticated APT is a growing challenge that is giving security professionals sleepless nights! But what are Advanced Persistent Threats? How do they work? How to detect APT attacks? Is it possible to prevent them?

Let us delve into the answers.

What is an Advanced Persistent Threat?

An Advanced Persistent Threat (APT) is a prolonged, clandestine, targeted, and sophisticated cyber-attack wherein the attacker gains unauthorized access to a system/network, establishes illicit presence, and remains undetected for prolonged time periods.

Unlike traditional application threats, attackers do not want to get in and out quickly in APT attacks. They seek to gain and maintain continuous access to the systems/network for prolonged durations.


Though the ultimate goal of mining highly sensitive data over prolonged time periods, the consequences vary widely.

  • Gain access to Intellectual Property for massive competitive advantages.
  • Listening to state / trade / defense secrets or gather intelligence.
  • Sabotage of critical infrastructure (alter product lines, delete complete databases, etc.)
  • Complete site/application takeover.

The Targets

These attacks are typically targeted against high-value targets such as nation-states, large corporations, financial institutions, defense organizations, government agencies and networks, and so on. The attackers engage in extensive research before choosing a target.

How Do Advanced Persistent Threats Work? 

Stage 1: Infiltration 

In this stage, attackers look to gain access and establish their presence within the network/ application. They target and seek to infiltrate one of three attack surfaces, namely – authorized human users, web assets, or network resources.

To this end, they leverage social engineering, injection attacks, or other application vulnerabilities to insert malware into the target. They may simultaneously orchestrate DDoS attacks as a smokescreen to distract IT security personnel and further weaken the security defenses.

Then, the attackers exploit the malware to create backdoors, shells, and tunnels that not just grant them access to the networks/systems, but also allows them to move around clandestinely.

Stage 2: Expansion of Foothold / Presence

After successfully gaining access to the network, the attackers look to broaden their presence and deepen their access through password cracking, gaining administrative privileges, etc. Doing so, they wield greater control over the systems/ network to do their bidding. For instance, breaching accounts of members at higher levels of the organizational hierarchy enables attackers to gain access to more sensitive data.

Stage 3: Extraction of Data 

Attackers typically encrypt, compress, and store stolen data in secure locations in the network itself. Once they have accumulated enough data, they need to exfiltrate it without being detected and transfer it to their own systems. Attackers typically use white noise techniques and DDoS attacks to distract the IT security team and weaken the defenses to harvest the data.

The backdoors/ tunnels enable them to remain undetected for prolonged durations and repeat the process.

How to Detect APT Attacks? 

Though advanced persistent threat detection is challenging, it is not impossible. Here are some warning signs that enable APT threat detection:

  • Unusual activity in user accounts such as an increase in late-night logins.
  • Unusual database activities such as massive data flow from internal sources to internal or external systems, data stored/ archived in unusual locations, presence of unusual data files, etc.
  • Widespread backdoor Trojans
  • Presence of password-hashes stolen from password-hash-storage databases or memory.

How to Prevent Advanced Persistent Threats? 

Traditional security measures such as firewalls, anti-virus, and anti-malware are not equipped to prevent APT attacks. For Advanced Persistent Threat Prevention, you must employ an intelligent and multi-layered approach.

  • Employing a managed, intuitive WAF such as the one from AppTrana at the network perimeter will enable you to monitor all incoming traffic and requests. WAFs filter out malicious traffic and virtually patch vulnerabilities to ensure that attackers don’t leverage them. They also help stop common attacks such as SQL injections, RFI, DDoS, etc. often used during stage 1 of APT attacks.
  • Internal traffic monitoring using network firewalls will enable you to identify traffic abnormalities that indicate an ongoing attack, system honeypots, backdoors, etc.
  • Application and domain whitelisting ensure that only trusted domains are accessed, and applications/ software installed by the users. This helps reduce the success rate of APT attacks.
  • For whitelisting to be effective, strict update policies must be enforced as outdated software and applications are vulnerable to attacks.
  • Enforce strong access controls and multi-factor authentication.
  • Email protection to prevent spam and phishing attacks.
  • Ongoing employee and stakeholder education.


Having found the answer to what are advanced persistent threats, you will understand that APT threat detection is challenging and that advanced persistent threat prevention is imperative for heightened security. Advanced persistent threat solutions from expert security service providers like AppTrana will enable you to prevent APT attacks from happening and fortify your overall security posture.