What is an attack vector? How attackers get into your systems

What is an attack vector?

An attack vector is the specific route an attacker takes to breach your defenses. If a vulnerability is the unlocked door and an exploit is the act of opening it, the attack vector is the hallway the attacker walks down to reach that door.

Common attack vectors include:

Phishing and social engineering. Tricking humans into clicking malicious links, opening infected attachments, or sharing credentials. According to Keepnet, an estimated 3.4 billion phishing emails are sent daily, making it the most common initial attack vector.
Unpatched vulnerabilities. Exploiting known software flaws that haven't been remediated. This is where vulnerability scanning, CVSS, EPSS, and KEV come in.
Compromised credentials. Using stolen, leaked, or brute-forced passwords to authenticate as a legitimate user. Credential stuffing and password spraying attacks target this vector.
Misconfigured services. Exploiting cloud resources, databases, or APIs left exposed through misconfiguration. Publicly accessible S3 buckets, open database ports, and overly permissive IAM roles all fall here.
Supply chain. Compromising a trusted third-party component (an open-source library, a SaaS integration, a vendor's update mechanism) to gain access to downstream targets.
Insider threats. Malicious or negligent actions by employees, contractors, or partners with legitimate access.

Why attack vectors matter for startups

Understanding attack vectors helps you allocate your limited security resources to the entry points attackers actually use, rather than defending against theoretical threats.

Your attack surface determines your vectors. A startup with a web application, cloud infrastructure, and a remote team has different attack vectors than a hardware company with a physical office. Map your attack surface first, then identify which vectors apply.
Most breaches use a small set of vectors. According to Verizon's 2025 Data Breach Investigations Report, the majority of breaches involve credentials, phishing, or exploitation of vulnerabilities. You don't need to defend against everything, just the vectors most relevant to your technology stack and threat model.
Each vector maps to specific controls. Phishing maps to email filtering and security awareness training. Unpatched vulnerabilities map to scanning and patch management. Misconfigurations map to CSPM and infrastructure-as-code reviews. Knowing your vectors tells you where to invest.
CVSS uses attack vector as a scoring factor. The CVSS base score includes "Attack Vector" as a metric: Network (remotely exploitable), Adjacent (requires shared network), Local (requires local access), or Physical (requires physical access). Network-vector vulnerabilities are scored higher because they're accessible to the most attackers.

How Fencer helps reduce attack vectors

Fencer addresses multiple attack vectors simultaneously. SAST catches code-level vulnerabilities before they reach production. CSPM detects misconfigurations that expose cloud services. EASM discovers external-facing assets attackers can target. By covering code, cloud, and perimeter in a single platform, Fencer helps startups systematically reduce the attack paths available to adversaries.

Frequently asked questions

What's the difference between an attack vector and an attack surface?

An attack vector is the specific path or method an attacker uses to breach your systems (like phishing, an unpatched vulnerability, or a compromised credential). An attack surface is the total collection of all possible attack vectors available to an attacker. Think of it this way: each unlocked window or open door is an attack vector. The entire exterior of your building, with all its potential entry points, is the attack surface. Reducing your attack surface means eliminating or securing individual attack vectors.

What is the most common attack vector?

Phishing and credential-based attacks consistently rank as the most common initial attack vectors. Verizon's Data Breach Investigations Report finds that credentials and phishing account for the majority of initial access in confirmed breaches. For startups specifically, misconfigured cloud services are also a significant vector because rapid infrastructure provisioning often outpaces security review. The relative importance of each vector depends on your specific technology stack and threat model.

How do I identify which attack vectors apply to my startup?

Start by mapping your attack surface: what systems are internet-facing, how do users authenticate, what third-party services do you integrate with, and where does sensitive data flow. Then assess each common vector against your environment. If you have a web application, test for web-based vectors (injection, authentication flaws). If you use cloud infrastructure, audit for misconfigurations. If your team handles sensitive data via email, assess phishing susceptibility. EASM tools can help discover external attack vectors you may not be aware of. The goal is to prioritize vectors based on your actual exposure, not a generic threat list.

Attack Vector