How Attackers Gain Initial Access to a Business Network

At 2:47 in the morning, a login succeeds on a company’s remote access portal. It does not look alarming: a valid username, a valid password, a connection that resembles an employee working late from home. But no employee is working. The password belonged to someone who had reused it on a personal account breached months earlier, and the person now using it is an intruder who just crossed the line from outside the network to inside it. Nothing was forced. The attacker simply walked through a door using a key that was lying around. This moment, the first foothold inside a network, is called initial access, and it is the hinge on which nearly every breach turns.

Initial access is the stage where an attacker first gets in. Everything dramatic that follows, stolen data, ransomware, a business shut down, depends on this first step succeeding, which is why it is both the attacker’s primary objective early on and the defender’s best opportunity to stop an attack before it starts. Understanding the handful of ways attackers typically get that first foothold is what lets a business close the doors that matter most.

The Main Ways Attackers Get In #

Most initial access traces back to a small number of recurring entry points. They are worth knowing because each has a specific defense.

• Stolen or weak credentials. The most common path, and often the easiest. An attacker logs in with a username and password obtained from a breach, bought from an underground market, or guessed because it was weak or reused. From the system’s point of view, nothing is wrong: it is a valid login. This is why a leaked password is so dangerous, it turns breaking in into simply signing in.
• Exploiting unpatched systems. Software with a known security flaw that has not been updated is an open window. Attackers actively scan the internet for systems running vulnerable versions of widely used software, particularly internet-facing things like remote access tools, web applications, and firewalls, and walk in through the gap a patch would have closed.
• Tricking a person. A deceptive email or message that gets someone to enter their credentials on a fake page, or to run a malicious attachment, hands the attacker their entry. The mechanics of how these messages manipulate are a subject of their own, but the outcome is a foothold.

Across all three, a pattern stands out: attackers strongly prefer to log in rather than break in. Valid credentials and unpatched-but-legitimate access points are quieter and more reliable than forcing anything, which is why so much of initial access comes down to credentials and patches rather than dramatic hacking.

Why This Stage Matters Most #

Initial access is the narrowest point in an attack, and that is what makes it the most valuable place to defend. Before an attacker is in, they are outside, with limited options and high uncertainty. Once they have a foothold, their options multiply quickly and the defender’s job gets much harder. Stopping the entry is far cheaper than untangling everything that can follow it.

It is also the stage where defenses are most concrete. The entry points are known and finite, which means they can be systematically closed. What happens after a foothold is established, how an attacker expands their access and moves toward their goal, is a separate stage with its own dynamics, but none of it happens if the first foothold is denied. Initial access is where prevention has the most leverage.

Closing the Main Doors #

Because the common entry points are few, the defenses that matter most are correspondingly focused. Multi-factor authentication is the single highest-value measure, because it directly defeats the most common vector: a stolen password alone no longer grants entry when a second factor is required. Disciplined patching closes the second major door, keeping internet-facing software updated removes the known vulnerabilities attackers scan for. Strong, unique passwords and removing unused accounts shrink the credential attack surface further.

These measures share a logic: they make the easy paths hard. Attackers favor initial access techniques precisely because they are low-effort and reliable, so raising the effort, requiring a second factor, eliminating the unpatched window, denying the reused password, pushes many attackers toward targets that did not bother. The business that closes its main doors is not invulnerable, but it is no longer the easy mark that opportunistic attacks depend on. What an attacker attempts once inside, and why containment matters even after entry, is the next part of the picture.

Frequently Asked Questions #

What is the most common way attackers get into a network?
Stolen or weak credentials, by a wide margin. Rather than using sophisticated exploits, most attackers simply log in with a username and password that was breached elsewhere, reused, bought from an underground market, or weak enough to guess. From the system’s perspective it looks like a legitimate login, which is exactly what makes it both effective for attackers and preventable with measures like multi-factor authentication.

If attackers just log in with stolen passwords, how does MFA help?
Multi-factor authentication requires a second proof of identity beyond the password, a code, an app approval, a hardware key, so a stolen password by itself is not enough to get in. Since stolen credentials are the most common entry vector, this single measure neutralizes a large share of initial access attempts. It is not perfect, but it converts the easiest attack path into a much harder one.

Why does unpatched software matter so much for security?
When a software vulnerability becomes publicly known, attackers begin scanning the internet for systems that have not yet applied the fix, especially internet-facing systems like VPNs, web servers, and firewalls. An unpatched system is a known, documented way in, requiring little skill to exploit. Timely patching closes these windows before attackers can use them, which is why it is one of the most important security habits.

Is initial access the same as a full breach?
No, it is the first step toward one. Initial access is the moment an attacker establishes a foothold, but it is what they do afterward, expanding access, locating valuable data, deploying ransomware, that turns a foothold into a damaging breach. This is also why initial access is such an important place to defend: stopping it prevents everything downstream, and even when entry occurs, limiting what an attacker can do next is a separate and crucial layer.