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Advanced Persistent Threats What is an Advanced Persistent Threat (APT)? - Stages and Examples
If you are reading this blog, it only means one thing: you already have a basic idea about Advanced Persistent Threats (APTs) and are eager to understand this complex and stealthy cyber threat better. This blog will help deepen your understanding of how APTs operate, why they’re so dangerous, and what organizations do to defend against these threats.
Let us start with the main characters in this concept: Threat Actors. They are a group of people who take part in malicious acts in cyber realms (can include anything that connects to the cloud; computers, devices, systems, networks).
Now, what does Advanced Persistent Threats (APTs) actually mean?
When these threat actors target an organisation/state and gains unauthorised access to the organisation’s system network and remains undetected for a long period of time, the concept of APT comes into picture.
If you could compare APTs to typical cyber-attacks, they would be the top of the cyber chain. The threat actors basically stick to their targets and not leave them until they are satisfied. Unlike cyber-attacks, where the victims are attacked and it is done and dusted after. These threat actors use advanced tools and techniques to sneak into their victims’ network. Then they start observing and find a hidden access to their victims. Then they stay in their system and act like they belong there, a spy and get all the required information they want without noticing. Their main targets include governments, large enterprises, or critical infrastructure organizations.
These threat actors invest a large amount of time and resources to hold their place in the victims’ network. This helps them to slowly access any information without raising an alarm. They use a combination of custom malware, social engineering (like spear-phishing), and zero-day exploits (a cyber-attack that takes advantage of a previously unknown security vulnerability in software or hardware) to gain and maintain access while evading detection.
To help you understand it with an example. A thief who came to rob your house. If this thief gets into your house, finds what they want and leaves after leaving a mess. Then this can be compared to a typical cyberattack. During a normal cyber-attack, they hack a system and steal information (or whatever they desire) secretly and leave quite a big impact to the public eyes.
But imagine if this thief is patient. He finds a tiny open window (small weakness in your network) and uses the same to keep track of your daily routine, learns where you keep your valuables. And slowly take your valuables without you noticing anything.
That sneaky, patient thief is exactly how an Advanced Persistent Threat works in today’s network set up. Quietly sneaking into a network, staying hidden, and slowly stealing valuable information over a long time.
What are the stages of an APT attack?
When we talk about Advanced Persistent Threats (APTs), we’re talking about something higher than champions of the cybercrime world. These aren’t smash-and-grab attacks. APTs are slow, patient, and targeted. They creep into a network, spread like ivy through the walls, and quietly siphon off valuable data.
But here’s a catch, depending on who you ask, the “stages” of an APT attack might look a little different.
Some sources boil it down into 3 clear steps, while others expand it into 5 stages. Both are right though, they’re just different zoom levels of the same picture.
The 3-Stage Model (Simplified View)
This version trims APTs down to their most visible, high-level movements:
- Stage 1 : Infiltration The attackers get in, often through aimed spear-phishing emails focusing on high-value targets like executives or IT leaders. These emails are customized, usually stolen to appear legit. Once someone clicks, the attackers slip past the main gate.
- Stage 2: Escalation & Lateral Movement Now inside, they often establish backdoors to ensure they can return even if one entry point is shut. After which they install malware, harvest credentials, and spread across the network.
- Stage 3: Exfiltration After collecting enough sensitive data, attackers move it out of the network, sometimes using diversion tactics (denial-of-service (DoS)) attacks to distract defenders. The network often remains compromised, waiting for the intruders’ return.
This model is clean and easy to explain to non-technical stakeholders, i.e; break in, spread out, steal.
The 5-Stage Model (Detailed View)
First let us understand MITRE ATT&CK also called Adversarial Tactics, Techniques & Common Knowledge is a global knowledge base that documents how real-world attackers operate once they are inside a network.
Think of it as a giant encyclopaedia of cybercriminal playbook: it doesn’t just say “bad guys hack networks” it tells you how, in detail, step by step, based on real-world incidents.
The name comes from MITRE Corporation, which is a non-profit that works on defence, cybersecurity and R&D.
The 5-stage version shows how security analysts and frameworks like MITRE ATT&CK describe the attack lifecycle:
Phishing, stolen credentials, or exploited vulnerabilities. The attackers’ foot in the door.
Malware or backdoors are installed to ensure persistence.
Attackers climb the access ladder, hop between systems, map the network, and seek high-value targets.
Sensitive data is quietly packaged up and smuggled out.
APTs are “persistent” for a reason — they keep backdoors open, ready to return when needed.
This model captures the stealth and persistence that make APTs so dangerous.
Techniques Used for APT attack
So these actors are probably Oscar winners for sure. They will blend into your network and act normal like they belong there, this will have them blend to the system seamlessly.
Let's explore what they use to blend in and get into your system step by step.
1. Initial Penetration to Your Network
During Initial process to penetrate to your network.
Spear-phishing emails
Malicious attachments or links, tailored to execs or key staff.
Watering hole attacks
Compromising websites employees trust. They break into a website you trust and hide a bug there, so when you visit, boom! you're infected!
Exploiting vulnerabilities
Unpatched systems, VPN appliances, or web apps. This is when they find cracks in your software.
Stolen credentials
Via dark web or brute-force attacks.
2. Execution & Persistence
After entering the system, to stay in the system and be persistent
Malware / Remote Access Trojans (RATs)
Take the thief we were talking about earlier for example, when a thief hides a walkie talking in your bedroom to listen to you talk about where you left all the valuable things and connect to the valuables.
Web shells
Malicious scripts uploaded to compromised servers. Imagine sneaking a secret backdoor into your window so they can crawl in later.
Scheduled tasks / services
Creating recurring jobs to re-establish access. This is like when they set their alarm clock to secretly check on you in a particular time.
Living-off-the-land
Abusing built-in features to avoid detection. When the thief, instead of bringing their own noisy tools, they just help themselves your crayons and markers.
3. Privilege Escalation & Lateral Movement
Once they have made sure they are secure in the system; they need to spread out/ populate their presence
Pass-the-Hash / Pass-the-Ticket
Reusing stolen credentials across the network. Take the thief again, when he uses your apartment details to order or get access to any services that is eligible for you.
Keylogging
Capturing keystrokes to grab credentials. When the thief overhears you talk about your locker passcode or anything in general and note it down.
Exploiting misconfigurations
weak Active Directory settings, unsegmented networks.
Credential dumping
from LSASS memory or the SAM database. The thief finds the box where all the spare keys are hidden (Windows memory) and take them.
Remote desktop abuse
Using RDP to pivot across systems. That individual then borrows your car and uses it to drive into other houses to steal (other computers).
4. Command & Control
Then they advance to using their system to control the users
Encrypted C2 traffic
Hiding communication inside HTTPS or DNS queries. This is like when the thief uses invisible pens to write around your house to make it easier for their team to access when they come.
Domain fronting
Masking traffic by routing through legitimate services. Pretending to be talking to a nice, safe friend (like YouTube), but whispering to the bad guy behind them.
Custom backdoors
Tools designed to blend in with normal traffic. The thief makes a stair eventually through the window for easier access of the house.
5. Exfiltration
The next step involves them trying to access the network and taking control
Data staging
Storing stolen data in hidden internal locations first. They hide your valuables in your bag, only to take it out once the cameras are clear.
Exfiltration over HTTPS
Blending data theft with normal web traffic. This is when they hide within the crowd with your valuables.
Cloud storage abuse
Sending data to attacker-controlled cloud storage (Dropbox, Google Drive, etc.).
Tunnelling techniques
Using VPNs, SSH, or DNS tunnelling to sneak data out.
Examples of APTs
Like mentioned earlier, APT is not the average group of actors who you can take for granted. Advanced Persistent Threats (APTs) are a whole different beast. These are nation-state–backed, professional crews of cyber-thieves. They’ve hit governments, corporations, and critical infrastructure. They stay hidden for months/years only to surface when the victim is vulnerable.
These aren’t smash-and-grab jobs. They’re slow, deliberate, and often backed by nation-states with political, military, or financial goals.
And over the last two decades, APTs have rewritten the playbook for cyber conflict.
Which is a whole different level if you compare it to a normal attack. As in this kind, you can find no escape once they expose themselves. Let us explore a bit more about some iconic cyber heists in the history of mankind.
Mentioned below is timeline of the most famous APT operations till date.
Operation Aurora
The modern APT was introduced into the world with Operation Aurora. It started with the engineers of the biggest names in the Silicon Valley (google, yahoo, adobe, and more than 20 companies) realising something is wrong. They started noticing their master data (Source code, trade secrets, internal communications) getting past their defence and slipping off.
This is believed to be done by a state sponsored Chinese actors. They exploited Internet Explorer to infiltrate corporate networks.
The reason why Aurora grabbed the world attention, is not just their method, but the targets. Cyber-espionage wasn’t theoretical anymore. It was happening, and it was happening to Google, Adobe, Yahoo, Rackspace, Juniper Networks, titans of the tech world. And the fact that their target wasn’t credit cards or monetary, but intellectual property and government intelligence, the kind of data that would help them hold a country under their palm with their national power and technological dominance.
For Google, this was more than an intrusion. It was a political line in the sand. In January 2010, they did something rare: they went public, pointing fingers at China and threatening to shut down operations there. Mentioning how they won’t tolerate any kind of disrespect and will not back down even if they must spend millions for the same. It was one of the first times a corporate giant openly accused a nation-state of cyberattacks.
Aurora was the moment the world woke up to the reality: cyberspace wasn’t just for hackers in hoodies. It had become a geopolitical battlefield after.
Stuxnet, the Digital Weapon
The year 2010 took everyone by shock. This wasn’t just some theft/espionage. This was sabotage. This happened in Iran’s Nutanz nuclear facility. This left the engineers baffled.
What they didn’t realize was that a worm named Stuxnet had infiltrated their systems. Unlike previous malware that stole data or caused crashes, Stuxnet had a very specific, surgical mission, to sabotage Iran’s nuclear program.
The worm, allegedly created by the U.S. and Israel were delivered through infected USB drives, it made uranium centrifuges spin themselves to death, all while showing fake “everything’s fine” signals to operators. By the time anyone realized, hundreds of centrifuges were destroyed.
For the first time in history, a piece of code caused real-world destruction. Stuxnet proved that cyberspace could directly damage physical infrastructure and cyberweapons became a reality. Which is why it is considered the world’s first known cyber weapon
Stuxnet not only delayed Iran’s nuclear ambitions but also changed the rules of warfare. It showed the world that lines of code could cause physical destruction, blurring the line between cyberattacks and military operations.
Cozy Bear (APT29)
After Stuxnet came a very silent and quiet inflation. Instead of being loud and destructive, APT29 (Cozy Bear) which was discovered in the year 2015 shifted to espionage.
They were later discovered to be linked to Russia’s intelligence services. They didn’t have their primary focus on nuclear reactors or money, but information. They managed to get into the U.S. State Department, the Pentagon, and even unclassified White House systems.
Once inside, they blended in like they belong there. No noise. Didn’t break things. Nothing. Blended in and sat quietly acting normal like they belonged in the network, monitoring emails and communications, soaking up intelligence.
It was classic espionage. The digital version of wiretapping government offices. And because it was so subtle, the infiltration went unnoticed for months. By the time U.S. cybersecurity teams realized what had happened, Cozy Bear had already read vast amounts of sensitive material.
This was a reminder that cyberattacks don’t always aim for destruction. Sometimes, the most dangerous weapon is knowledge and Cozy Bear had plenty of it.
Fancy Bear (APT28)
That’s when APT28 (Fancy Bear), another Russia-linked group, hacked into the Democratic National Committee (DNC). They didn’t storm the gates with brute force; instead, slipped in with a humble-looking email.
A DNC employee received a spear-phishing email disguised as a Google security alert. “Click here to reset your password.”
Innocent enough, right? That single click opened the door for these threat actors.
Once inside, they stole tens of thousands of emails. And then came the masterstroke: they didn’t keep the loot hidden. They leaked it. Carefully timed releases made sure the emails hit headlines at pivotal moments during the U.S. election. Private conversations turned into scandals. News cycles spun. Narratives shifted.
This wasn’t theft. It was weaponized information. Fancy Bear proved that stolen data could be transformed into political ammunition. The attack forever changed the way we view elections: showing the world that an election could be influenced not by ballots but by bytes.
Lazarus Group
Now we shift from politics to pure money, but not the way you'd expect. As the Russians were leaking information; across the globe, North Korea's Lazarus Group had different ambitions. Instead of espionage, they went straight for the money.
In 2016, they launched one of the boldest bank heists in history. By infiltrating the Bangladesh Central Bank through the SWIFT system (the network used for international transfers), Lazarus tried to transfer nearly $1 billion into accounts around the world. Imagine, one of the most secretive nations on Earth trying to rob banks on a scale straight out of a Hollywood script.
The plan was nearly flawless. But fate (or rather a typo) got in the way. One of the fraudulent requests misspelled “foundation” as “fandation,” raising suspicions and halting many of the transfers. Even so, they successfully stole $81 million, much of it funnelled through Philippine casinos.
It was cybercrime on a Hollywood scale. Lazarus had shown that a nation-state could use hacking to fund its economy under sanctions. For North Korea, it wasn’t just crime, it was survival.
APT41
If hacking were a movie, APT41 would be the crew living double lives. Most APT groups serve a single purpose: espionage, sabotage, or theft. But APT41, a Chinese group, was different. They lived a double life.
By day, they acted as Chinese state-sponsored hackers, stealing intellectual property, targeting healthcare and telecom industries, and conducting surveillance on political dissidents. By night, they became entrepreneurs of the dark web. Hacking video game companies, stole virtual currencies, creating in-game items, selling them on underground markets and even ran digital scams for profit.
This dual role made APT41 one of the most versatile and unpredictable groups out there. They proved that the lines between cyberwarfare and cybercrime could blur, and that one group could serve both a government and its own wallets at the same time.
And that flexibility and unpredictability made them one of the most dangerous APTs in the world.
SolarWinds
The climax of our story comes in 2020, with one of the most sophisticated cyberattacks ever uncovered. Believed to be Russian born actors, compromised the update mechanism of SolarWinds Orion (widely used IT management platform). When SolarWinds pushed a routine software update to its clients, it unknowingly delivered a backdoor to thousands of networks.
The victims are believed to be the U.S. government agencies, Fortune 500 companies, and critical infrastructure providers. In total, around 18,000 organizations were exposed.
What made SolarWinds terrifying wasn’t just the scale. It was the elegance. Instead of breaking into each target individually, the attackers rode in on trusted software updates, basically a modern-day Trojan Horse where the enemy wheeled right in through the front gate, welcomed with open arms.
This attack highlighted how fragile global supply chains are and proved that even the most secure organizations are only as strong as the software they trust.
Conclusion
From Stuxnet spinning Iranian centrifuges into chaos to SolarWinds sneaking through trusted updates, APTs have evolved into a weapon of choice for nations.
They’re not quick attacks; they’re long games. Patient. Persistent. Strategic. And every time we think we’ve seen it all, a new chapter is written with brand new pages leaving us hanging, usually months or years before we even get to explore it.
Cybersecurity is no longer just an IT problem. It’s a geopolitical battlefield, where the lines between war, crime, and espionage blur more with each passing year.
The next big APT? It’s already happening. Somewhere out there, in some network we trust.
That’s where neXavault steps in. We’re not just building walls; we’re building watchtowers. We help you see threats coming before they knock, respond before they spread, and recover stronger than before.
Because in this story of cyber espionage, sabotage, and survival, your organization deserves to be the one that writes the ending, not suffers it.
neXavault: Turning persistence into protection.
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