Discover what an Advanced Persistent Threat (APT) is, how state-backed attackers use stealth and zero-days, and why they’re so hard to detect.
The first step in a cyberattack is often the most crucial, and also, unfortunately, the most overlooked. This phase, known as "initial access," is where attackers gain their first foothold in a network or system. It sets the stage for the entire attack chain, giving threat actors the opportunity to exploit vulnerabilities, steal data, or wreak havoc.
For cybersecurity professionals, understanding and defending against initial access is a must. This in-depth guide will explain the concept of initial access, highlight its importance, and walk you through how attackers use it, how to prevent it, and why it plays such a pivotal role in the modern cybersecurity landscape.
What is Initial Access in Cybersecurity?
Initial access refers to the attacker’s entry point into a victim’s network, system, or environment. Think of it as the proverbial "foot in the door." Once they’re in, attackers can advance through the cyber kill chain, escalating privileges, moving laterally through systems, and executing their malicious objectives.
This phase is central within frameworks like the Cyber Kill Chain and MITRE ATT&CK, where it’s categorized under the "Reconnaissance" tactic. By studying this stage, defenders can dissect the tactics, techniques, and procedures (TTPs) used by attackers to infiltrate systems, enabling them to fortify their defenses.
Why Initial Access Matters
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It’s the foundation of an attack: Without an entry point, the rest of the exploitative chain cannot occur.
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Early detection prevents escalation: Spotting initial access early on can reduce damage and prevent further breaches.
- Often overlooked: Many organizations focus on high-profile ransomware or data theft, but overlook the quieter, initial stage that enables it.
Common Initial Access Techniques
Attackers use a variety of methods to infiltrate networks. Here are the most prevalent ones, based on real-world attack trends and the MITRE ATT&CK framework.
1. Phishing and Spear Phishing
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What it is: Social engineering emails are designed to trick users into clicking malicious links or downloading harmful attachments.
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Example: An attacker posing as IT support emails an employee requesting that they reset their password using a malicious link.
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How to mitigate: Deploy email filters and conduct regular employee training to recognize phishing attempts. Start a free trial with Huntress Managed Security Awareness Training to see how we can help you.
2. Exploiting Public-Facing Applications
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What it is: Targeting unpatched vulnerabilities in internet-facing applications, such as web servers or APIs, to gain entry.
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Example: Exploiting a zero-day vulnerability in an enterprise’s web app to deploy malware.
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Mitigation: To mitigate these risks, having a tactical response team, like the Huntress SOC, provides a critical escalation point for handling intrusions.
3. Drive-By Compromises
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What it is: Using malicious websites or scripts to gain access when a user visits an infected page.
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Example: A user lands on a compromised site, which silently executes harmful scripts in their browser.
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How to mitigate: Keep website browsers up to date and implement robust endpoint detection tools.
4. Valid Accounts and Credential Theft
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What it is: Stealing or using leaked employee credentials to infiltrate systems.
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Example: Credential stuffing attacks using previously leaked usernames and passwords.
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How to mitigate: Enforce strong, unique passwords and implement multi-factor authentication (MFA).
5. Supply Chain Compromise
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What it is: Attacking third-party vendors or software providers to gain access to a target’s systems.
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Example: The SolarWinds breach, where attackers injected malware into legitimate software updates.
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How to mitigate: Vet suppliers carefully, monitor third-party access, and segment networks.
6. Malicious Removable Media
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What it is: Dropping infected USBs or drives in public places, tricking users into plugging them into their devices.
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Example: A USB marked "Confidential Project Plans" is left in a company’s parking lot, housing auto-executable malware.
- How to mitigate: Disable autorun features and educate employees on the risks of unknown devices.
Why Cybersecurity Professionals Can’t Ignore Initial Access
Sets the Stage for the Entire Attack
Without this initial foothold, cybercriminals can’t proceed with activities like lateral movement, privilege escalation, or data exfiltration. Think of initial access as opening the door; attackers can’t ransack the house unless they get inside first.
Early Detection Saves Time and Money
Catching breaches early reduces response costs, prevents downtime, and protects sensitive data. Studies show that identifying attacks in the initial stages can save millions of dollars compared to responding later in the kill chain.
Critical to Defense-in-Depth and Zero Trust Strategies
Defense-in-depth and Zero Trust approaches both prioritize fortifying every layer of your security, starting with securing entry points. You can’t ignore initial access if you’re serious about holistic cybersecurity.
Top Initial Access Vectors
A quick glance at the data shown above shows that Remote Desktop Protocol (RDP) and VPN logins top the list of initial access methods, closely followed by exposed external perimeters.
These numbers come with some caveats:
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Cases where the initial access vector couldn’t be determined (due to missing or incomplete telemetry) are excluded.
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For VPN-related access, we’re only counting logins using stolen or compromised credentials, not exploits.
So while this sample isn't statistically representative of every attack, it paints a compelling picture.
Despite the industry’s intense focus on zero-day exploits, phishing, and vulnerabilities, these accounted for a relatively small portion of the intrusions we observed. That might seem surprising—until you consider things from the perspective of a threat actor.
Real-world examples of Initial Access attacks
1. SolarWinds Supply Chain Attack
Hackers infiltrated SolarWinds’ network and pushed malicious updates to customers, enabling access to countless organizations globally, including government entities.
2. Phishing Campaign Leading to Credential Theft
Threat actors will often rely on phishing emails as an initial access vector. At Huntress, we have observed attackers sending a phishing email masquerading as a legitimate brand, like DocuSign, which tricks users into handing over their credentials, as we outlined in this post.
3. Remote Desktop Protocol-Related Intrusions
As highlighted here, two of the most common initial access methods used by threat actors are Remote Desktop Protocol (RDP) and VPN. When dealing with RDP-related incidents, it's essential to understand how attackers exploit exposed perimeter systems. Learn how the Huntress Tactical Response team identifies and shuts down these threats
Detecting and Mitigating Initial Access
Detection Techniques
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Endpoint Detection & Response (EDR): Tools like Huntress Managed EDR can identify anomalies and block malicious activity.
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Email Filters: Advanced detectors can flag phishing messages or malware-laden attachments.
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Behavioral Analytics: AI-powered solutions can spot unusual login patterns or file access.
Mitigation Best Practices
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Conduct continuous employee training to identify and report social engineering tactics.
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Maintain consistent patch management to fix vulnerabilities before attackers exploit them.
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Implement network segmentation to limit potential lateral movement.
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Use MFA to add an extra layer of protection.
Leveraging the MITRE ATT&CK Framework for Defense
MITRE ATT&CK organizes various cyberattack techniques, with "Initial Access" being the first step. Notable techniques include phishing, exploiting public-facing applications (T1190), and valid accounts (T1078). Red teams and threat hunters can use MITRE ATT&CK to map and simulate real-world threats, strengthening prevention and response strategies.
Initial Access vs Other Stages of Attack
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Initial Access vs Privilege Escalation: Initial access provides entry; privilege escalation grants higher access to sensitive systems.
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Initial Access vs Lateral Movement: Initial access gets attackers inside, while lateral movement allows them to explore the network.
- Initial Access vs Persistence: Access is the first step, but maintaining persistence ensures attackers can return even after discovery.
FAQs for Initial Access
Initial access refers to the methods hackers use to infiltrate an organization's network as their first step in a cyberattack. This can involve techniques like phishing, exploiting vulnerabilities, or using compromised credentials.
Some popular techniques include phishing emails with malicious attachments, exploiting unpatched software vulnerabilities, remote access exploitation, or using stolen login details.
Initial Access Brokers (IABs) specialize in compromising networks and selling access to other cybercriminals. They enable quicker and more targeted attacks, which makes it crucial for organizations to secure their systems thoroughly.
“These initial access brokers will breach networks, look for credentials then will sell those credentials to other parties so that they don’t have to worry about the hard task of actually breaking into your network - they already have those credentials provided to them via the initial access broker,” said Anton Ovrutsky, principal threat hunting and response analyst with Huntress, in a SOC incident walkthrough video.
Initial access often serves as the entry point for ransomware attacks. Once attackers gain access, they can deploy ransomware to encrypt critical files and demand a ransom payment.
Businesses can prevent initial access threats by implementing strong network defenses such as firewalls, email security measures, MFA, regular system updates, and employee training on identifying phishing attempts.
Understanding initial access techniques helps organizations develop effective defense strategies. By focusing on entry-point threats, businesses can reduce the risk of full-scale cyberattacks.
Yes, tools like endpoint detection and response (EDR), intrusion detection systems (IDS), and vulnerability scanners can help identify and mitigate initial access threats early on.
Related Resources
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